diff --git a/HISTORY.rst b/HISTORY.rst
index cbfd100..93b6f4d 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -1,5 +1,9 @@
 Changelog
 ---------
+
+- Adds the ability to define registration windows for forms.
+  [href]
+
 0.32.0 (2018-02-21)
 ~~~~~~~~~~~~~~~~~~~
 
diff --git a/onegov/form/__init__.py b/onegov/form/__init__.py
index f5e7811..1a2fd60 100644
--- a/onegov/form/__init__.py
+++ b/onegov/form/__init__.py
@@ -23,6 +23,7 @@
     FormDefinition,
     FormFile,
     FormSubmission,
+    FormRegistrationWindow,
     PendingFormSubmission,
     CompleteFormSubmission
 )
@@ -48,6 +49,7 @@
     'FormDefinitionCollection',
     'FormExtension',
     'FormFile',
+    'FormRegistrationWindow',
     'FormSubmission',
     'FormSubmissionCollection',
     'merge_forms',
diff --git a/onegov/form/collection.py b/onegov/form/collection.py
index 9d45f64..636085f 100644
--- a/onegov/form/collection.py
+++ b/onegov/form/collection.py
@@ -3,12 +3,14 @@
 from datetime import datetime, timedelta
 from onegov.core.crypto import random_token
 from onegov.core.utils import normalize_for_url
+from onegov.core.collection import GenericCollection
 from onegov.file.utils import as_fileintent
 from onegov.form.errors import UnableToComplete
 from onegov.form.fields import UploadField
 from onegov.form.models import (
     FormDefinition,
     FormSubmission,
+    FormRegistrationWindow,
     FormFile
 )
 from sedate import replace_timezone, utcnow
@@ -30,6 +32,10 @@ def definitions(self):
     def submissions(self):
         return FormSubmissionCollection(self.session)
 
+    @property
+    def registration_windows(self):
+        return FormRegistrationWindowCollection(self.session)
+
     def scoped_submissions(self, name, ensure_existance=True):
         if not ensure_existance or self.definitions.by_name(name):
             return FormSubmissionCollection(self.session, name)
@@ -134,7 +140,7 @@ def query(self):
         return query
 
     def add(self, name, form, state, id=None, payment_method=None,
-            meta=None, email=None):
+            meta=None, email=None, spots=None):
         """ Takes a filled-out form instance and stores the submission
         in the database. The form instance is expected to have a ``_source``
         parameter, which contains the source used to build the form (as only
@@ -161,6 +167,14 @@ def add(self, name, form, state, id=None, payment_method=None,
                 self.session.query(FormDefinition)
                     .filter_by(name=name).one())
 
+        if definition is None:
+            registration_window = None
+        else:
+            registration_window = definition.current_registration_window
+
+        if registration_window:
+            assert registration_window.accepts_submissions
+
         # look up the right class depending on the type
         submission_class = FormSubmission.get_polymorphic_class(
             state, FormSubmission
@@ -172,6 +186,8 @@ def add(self, name, form, state, id=None, payment_method=None,
         submission.state = state
         submission.meta = meta or {}
         submission.email = email
+        submission.registration_window = registration_window
+        submission.spots = spots
         submission.payment_method = (
             payment_method or
             definition and definition.payment_method or
@@ -371,3 +387,22 @@ def delete(self, submission):
         """ Deletes the given submission and all the files belonging to it. """
         self.session.delete(submission)
         self.session.flush()
+
+
+class FormRegistrationWindowCollection(GenericCollection):
+
+    def __init__(self, session, name=None):
+        super().__init__(session)
+        self.name = name
+
+    @property
+    def model_class(self):
+        return FormRegistrationWindow
+
+    def query(self):
+        query = super().query()
+
+        if self.name:
+            query = query.filter_by(FormRegistrationWindow.name == self.name)
+
+        return query
diff --git a/onegov/form/models/__init__.py b/onegov/form/models/__init__.py
index d3b56c3..864e2d9 100644
--- a/onegov/form/models/__init__.py
+++ b/onegov/form/models/__init__.py
@@ -3,9 +3,11 @@
 from onegov.form.models.submission import PendingFormSubmission
 from onegov.form.models.submission import CompleteFormSubmission
 from onegov.form.models.submission import FormFile
+from onegov.form.models.registration_window import FormRegistrationWindow
 
 __all__ = (
     'FormDefinition',
+    'FormRegistrationWindow',
     'FormSubmission',
     'PendingFormSubmission',
     'CompleteFormSubmission',
diff --git a/onegov/form/models/definition.py b/onegov/form/models/definition.py
index 8a32aae..9887b3e 100644
--- a/onegov/form/models/definition.py
+++ b/onegov/form/models/definition.py
@@ -3,6 +3,7 @@
 from onegov.core.orm.mixins import meta_property, content_property
 from onegov.core.utils import normalize_for_url
 from onegov.form.models.submission import FormSubmission
+from onegov.form.models.registration_window import FormRegistrationWindow
 from onegov.form.parser import parse_form
 from onegov.form.utils import hash_definition
 from onegov.form.extensions import Extendable
@@ -62,6 +63,48 @@ class FormDefinition(Base, ContentMixin, TimestampMixin, SearchableDefinition,
     #: link between forms and submissions
     submissions = relationship('FormSubmission', backref='form')
 
+    #: link between forms and registration windows
+    registration_windows = relationship(
+        'FormRegistrationWindow',
+        backref='form',
+        order_by='FormRegistrationWindow.start')
+
+    #: the currently active registration window
+    #:
+    #: this sorts the registration windows by the smaller k-nearest neighbour
+    #: result of both start and end in relation to the current date
+    #:
+    #: the result is the *nearest* date range in relation to today:
+    #: * during an active registration window, it's that active window
+    #: * outside of active windows, it's last window half way until
+    #:   the next window starts
+    #:
+    #: this could of course be done more conventionally, but this is cooler 😅
+    current_registration_window = relationship(
+        'FormRegistrationWindow', viewonly=True, uselist=False,
+        primaryjoin="""and_(
+            FormRegistrationWindow.name == FormDefinition.name,
+            FormRegistrationWindow.id == select((
+                FormRegistrationWindow.id,
+            )).where(
+                FormRegistrationWindow.name == FormDefinition.name
+            ).order_by(
+                func.least(
+                    cast(
+                        func.now().op('AT TIME ZONE')(
+                            FormRegistrationWindow.timezone
+                        ), Date
+                    ).op('<->')(FormRegistrationWindow.start),
+                    cast(
+                        func.now().op('AT TIME ZONE')(
+                            FormRegistrationWindow.timezone
+                        ), Date
+                    ).op('<->')(FormRegistrationWindow.end)
+                )
+            ).limit(1)
+        )"""
+    )
+
     #: lead text describing the form
     lead = meta_property()
 
@@ -99,3 +142,14 @@ def has_submissions(self, with_state=None):
             query = query.filter(FormSubmission.state == with_state)
 
         return query.first() and True or False
+
+    def add_registration_window(self, start, end, **options):
+        window = FormRegistrationWindow(
+            start=start,
+            end=end,
+            **options
+        )
+
+        self.registration_windows.append(window)
+
+        return window
diff --git a/onegov/form/models/registration_window.py b/onegov/form/models/registration_window.py
new file mode 100644
index 0000000..2c3cb03
--- /dev/null
+++ b/onegov/form/models/registration_window.py
@@ -0,0 +1,151 @@
+import sedate
+
+from onegov.core.orm import Base
+from onegov.core.orm.mixins import TimestampMixin
+from onegov.core.orm.types import UUID
+from sqlalchemy import Boolean, Column, Date, ForeignKey, Integer, Text, text
+from sqlalchemy.dialects.postgresql import ExcludeConstraint
+from sqlalchemy.schema import CheckConstraint
+from sqlalchemy.sql.elements import quoted_name
+from sqlalchemy.orm import object_session, relationship
+from uuid import uuid4
+
+
+daterange = Column(quoted_name('DATERANGE("start", "end")', quote=False))
+
+
+class FormRegistrationWindow(Base, TimestampMixin):
+    """ Defines a registration window during which a form definition
+    may be used to create submissions.
+
+    Submissions created thusly are attached to the currently active
+    registration window.
+
+    Registration windows may not overlap.
+
+    """
+
+    __tablename__ = 'registration_windows'
+
+    #: the public id of the registraiton window
+    id = Column(UUID, primary_key=True, default=uuid4)
+
+    #: the name of the form to which this registration window belongs
+    name = Column(Text, ForeignKey("forms.name"), nullable=False)
+
+    #: true if the registration window is enabled
+    enabled = Column(Boolean, nullable=False, default=True)
+
+    #: the start date of the window
+    start = Column(Date, nullable=False)
+
+    #: the end date of the window
+    end = Column(Date, nullable=False)
+
+    #: the timezone of the window
+    timezone = Column(Text, nullable=False, default='Europe/Zurich')
+
+    #: the number of spots (None => unlimited)
+    limit = Column(Integer, nullable=True)
+
+    #: enable an overflow of submissions
+    overflow = Column(Boolean, nullable=False, default=True)
+
+    #: submissions linked to this
+    submissions = relationship('FormSubmission', backref='registration_window')
+
+    __table_args__ = (
+
+        # ensures that there are no overlapping date ranges within one form
+        ExcludeConstraint(
+            (name, '='), (daterange, '&&'),
+            name='no_overlapping_registration_windows',
+            using='gist'
+        ),
+
+        # ensures that there are no adjacent date ranges
+        # (end on the same day as next start)
+        ExcludeConstraint(
+            (name, '='), (daterange, '-|-'),
+            name='no_adjacent_registration_windows',
+            using='gist'
+        ),
+
+        # ensures that start <= end
+        CheckConstraint(
+            '"start" <= "end"',
+            name='start_smaller_than_end'
+        ),
+    )
+
+    @property
+    def localized_start(self):
+        return sedate.align_date_to_day(
+            sedate.standardize_date(
+                sedate.as_datetime(self.start), self.timezone
+            ), self.timezone, 'down'
+        )
+
+    @property
+    def localized_end(self):
+        return sedate.align_date_to_day(
+            sedate.standardize_date(
+                sedate.as_datetime(self.end), self.timezone
+            ), self.timezone, 'up'
+        )
+
+    @property
+    def accepts_submissions(self):
+        if not self.enabled:
+            return False
+
+        if not self.in_the_present:
+            return False
+
+        if self.overflow:
+            return True
+
+        if self.limit is None:
+            return True
+
+        return self.available_spots > 0
+
+    def disassociate(self):
+        """ Disassociates all records linked to this window. """
+
+        for submission in self.submissions:
+            submission.registration_window_id = None
+
+    @property
+    def available_spots(self):
+        return self.limit - self.claimed_spots - self.requested_spots
+
+    @property
+    def claimed_spots(self):
+        return object_session(self).execute(text("""
+            SELECT SUM(COALESCE(claimed, 0))
+            FROM submissions
+            WHERE registration_window_id = :id
+            AND submissions.state = 'complete'
+        """), {'id': self.id}).scalar() or 0
+
+    @property
+    def requested_spots(self):
+        return object_session(self).execute(text("""
+            SELECT SUM(GREATEST(COALESCE(spots, 0) - COALESCE(claimed, 0), 0))
+            FROM submissions
+            WHERE registration_window_id = :id
+            AND submissions.state = 'complete'
+        """), {'id': self.id}).scalar() or 0
+
+    @property
+    def in_the_future(self):
+        return sedate.utcnow() <= self.localized_start
+
+    @property
+    def in_the_past(self):
+        return self.localized_end <= sedate.utcnow()
+
+    @property
+    def in_the_present(self):
+        return self.localized_start <= sedate.utcnow() <= self.localized_end
diff --git a/onegov/form/models/submission.py b/onegov/form/models/submission.py
index dc24ba3..e82238f 100644
--- a/onegov/form/models/submission.py
+++ b/onegov/form/models/submission.py
@@ -12,7 +12,7 @@
 from onegov.pay import Payable
 from onegov.pay import process_payment
 from sedate import utcnow
-from sqlalchemy import Column, Enum, ForeignKey, Text
+from sqlalchemy import Column, Enum, ForeignKey, Integer, Text
 from sqlalchemy_utils import observes
 from uuid import uuid4
 from wtforms import StringField, TextAreaField
@@ -63,6 +63,20 @@ class FormSubmission(Base, TimestampMixin, Payable, AssociatedFiles,
         nullable=False
     )
 
+    #: the number of spots this submission wants to claim
+    #: (only relevant if there's a registration window)
+    spots = Column(Integer, nullable=False, default=0)
+
+    #: the number of spots this submission has actually received
+    #: None => the decision if spots should be given is still open
+    #: 0 => the decision was negative, no spots were given
+    #: 1-x => the decision was positive, at least some spots were given
+    claimed = Column(Integer, nullable=True, default=None)
+
+    #: the registration window linked with this submission
+    registration_window_id = Column(
+        UUID, ForeignKey("registration_windows.id"), nullable=True)
+
     #: payment options -> copied from the dfinition at the moment of
     #: submission. This is stored alongside the submission as the original
     #: form setting may change later.
diff --git a/onegov/form/tests/test_model.py b/onegov/form/tests/test_model.py
index 376f951..65f1b7a 100644
--- a/onegov/form/tests/test_model.py
+++ b/onegov/form/tests/test_model.py
@@ -1,10 +1,16 @@
 import pytest
 
+from datetime import date, timedelta
 from onegov.form import FormCollection, FormExtension
+from sqlalchemy.exc import IntegrityError
 from webob.multidict import MultiDict
 from wtforms import ValidationError
 
 
+def days(d):
+    return timedelta(days=d)
+
+
 def test_has_submissions(session):
     collection = FormCollection(session)
     form = collection.definitions.add('Newsletter', definition="E-Mail = @@@")
@@ -77,3 +83,171 @@ class ExtendedForm(self.form_class, CorporateOnly):
     submission = collection.submissions.add(
         'members', form, state='complete')
     assert issubclass(submission.form_class, CorporateOnly)
+
+
+def test_registration_window_adjacent(session):
+    forms = FormCollection(session)
+
+    summer = forms.definitions.add('Summercamp', definition="E-Mail = @@@")
+    winter = forms.definitions.add('Witnercamp', definition="E-Mail = @@@")
+
+    summer.add_registration_window(date(2017, 4, 1), date(2017, 6, 30))
+    summer.add_registration_window(date(2018, 4, 1), date(2018, 6, 30))
+
+    assert len(summer.registration_windows) == 2
+
+    winter.add_registration_window(date(2017, 4, 1), date(2017, 6, 30))
+    winter.add_registration_window(date(2018, 4, 1), date(2018, 6, 30))
+
+    assert len(winter.registration_windows) == 2
+
+    # no overlap -> different forms
+    session.flush()
+
+    # adjacent, fails
+    summer.add_registration_window(date(2017, 1, 1), date(2017, 4, 1))
+
+    with pytest.raises(IntegrityError) as e:
+        session.flush()
+
+    assert 'no_adjacent_registration_windows' in str(e)
+
+
+def test_registration_window_overlaps(session):
+    forms = FormCollection(session)
+
+    summer = forms.definitions.add('Summercamp', definition="E-Mail = @@@")
+    summer.add_registration_window(date(2017, 4, 1), date(2017, 6, 30))
+
+    assert len(summer.registration_windows) == 1
+
+    # no overlap -> different forms
+    session.flush()
+
+    # overlapping, fails
+    summer.add_registration_window(date(2017, 1, 1), date(2017, 4, 2))
+
+    with pytest.raises(IntegrityError) as e:
+        session.flush()
+
+    assert 'no_overlapping_registration_windows' in str(e)
+
+
+def test_registration_window_end_before_start(session):
+    camp = FormCollection(session).definitions.add(
+        'Camp', definition="E-Mail = @@@")
+
+    camp.add_registration_window(date(2018, 1, 1), date(2017, 1, 1))
+
+    with pytest.raises(IntegrityError) as e:
+        session.flush()
+
+    assert 'start_smaller_than_end' in str(e)
+
+
+def test_current_registration_window_bound_to_form(session):
+    forms = FormCollection(session)
+    today = date.today()
+
+    winter = forms.definitions.add('Witnercamp', definition="E-Mail = @@@")
+    winter.add_registration_window(today - days(1), today + days(1))
+
+    summer = forms.definitions.add('Summercamp', definition="E-Mail = @@@")
+    summer.add_registration_window(today - days(100), today - days(10))
+
+    assert winter.current_registration_window.start == today - days(1)
+    assert summer.current_registration_window.start == today - days(100)
+
+
+def test_current_registration_window_end_date(session):
+    forms = FormCollection(session)
+    today = date.today()
+
+    summer = forms.definitions.add('Summercamp', definition="E-Mail = @@@")
+
+    # the first window is closer, though the start is further away
+    summer.add_registration_window(today - days(10), today - days(1))
+    summer.add_registration_window(today + days(5), today + days(10))
+
+    assert summer.current_registration_window.start == today - days(10)
+
+
+def test_registration_window_spots(session):
+    forms = FormCollection(session)
+    today = date.today()
+
+    summer = forms.definitions.add('Summercamp', definition="E-Mail = @@@")
+    window = summer.add_registration_window(today - days(5), today + days(5))
+
+    session.flush()
+
+    window.enabled = False
+    assert not window.accepts_submissions
+
+    window.enabled = True
+    window.end = today - days(1)
+    assert not window.accepts_submissions
+
+    window.start = today + days(1)
+    window.end = today + days(5)
+    assert not window.accepts_submissions
+
+    window.start = today - days(5)
+    window.overflow = True
+    assert window.accepts_submissions
+
+    window.overflow = False
+    window.limit = None
+    assert window.accepts_submissions
+    assert window.claimed_spots == 0
+    assert window.requested_spots == 0
+
+    window.limit = 2
+    assert window.accepts_submissions
+    assert window.claimed_spots == 0
+    assert window.requested_spots == 0
+
+    s1 = forms.submissions.add(
+        name='summercamp',
+        form=summer.form_class(data={'e_mail': 'info@example.org'}),
+        state='complete',
+        spots=1
+    )
+
+    assert window.accepts_submissions
+    assert window.claimed_spots == 0
+    assert window.requested_spots == 1
+
+    s2 = forms.submissions.add(
+        name='summercamp',
+        form=summer.form_class(data={'e_mail': 'info@example.org'}),
+        state='complete',
+        spots=1
+    )
+
+    assert not window.accepts_submissions
+    assert window.claimed_spots == 0
+    assert window.requested_spots == 2
+
+    window.overflow = True
+    assert window.accepts_submissions
+
+    s1.claimed = 1
+    session.flush()
+
+    assert window.accepts_submissions
+    assert window.claimed_spots == 1
+    assert window.requested_spots == 1
+
+    window.overflow = False
+    assert not window.accepts_submissions
+
+    s2.claimed = 1
+    session.flush()
+
+    assert not window.accepts_submissions
+    assert window.claimed_spots == 2
+    assert window.requested_spots == 0
+
+    window.overflow = True
+    assert window.accepts_submissions
diff --git a/onegov/form/upgrade.py b/onegov/form/upgrade.py
index b64493c..b8ccfe1 100644
--- a/onegov/form/upgrade.py
+++ b/onegov/form/upgrade.py
@@ -5,14 +5,14 @@
 from depot.io.utils import FileIntent
 from io import BytesIO
 from onegov.core.crypto import random_token
-from onegov.core.orm.types import JSON
+from onegov.core.orm.types import JSON, UUID
 from onegov.core.upgrade import upgrade_task
 from onegov.core.utils import dictionary_to_binary
 from onegov.core.utils import normalize_for_url
 from onegov.form import FormDefinitionCollection
 from onegov.form import FormFile
 from onegov.form import FormSubmission
-from sqlalchemy import Column, Text
+from sqlalchemy import Column, Integer, Text
 
 
 @upgrade_task('Enable external form submissions')
@@ -123,3 +123,22 @@ def add_group_order_to_form_definitions(context):
         column=Column('order', Text, nullable=False, index=True),
         default=lambda form: normalize_for_url(form.title)
     )
+
+
+@upgrade_task('Add registration window columns')
+def add_registration_window_columns(context):
+    context.operations.add_column(
+        'submissions',
+        Column('claimed', Integer, nullable=True)
+    )
+
+    context.operations.add_column(
+        'submissions',
+        Column('registration_window_id', UUID, nullable=True)
+    )
+
+    context.add_column_with_defaults(
+        table='submissions',
+        column=Column('spots', Integer, nullable=False),
+        default=0
+    )