refs #884. TZ for exports.

docs/userguide.rst

@@ -252,14 +252,16 @@ To export:
   * Select the file type you want (.csv is recommended; .xlsx types will also be
     easily accessible).
 
-  * Select the export file size you want, based on number of posts per file. Note that
-    larger file sizes will take longer to download.
+  * Select the export file size you want, based on number of posts per file. You may want to select
+    a number of posts that will work the program that you will be loading the data into, e.g., Excel.
 
   * Select Deduplicate if you only want one instance of every post. This will clean
     up your data, but will make the export take longer.
 
   * Item start date/end date allow you to limit the export based on the date
-    each post was created.
+    each post was created. Note that the date you enter will be in the local timezone. The date
+    in posts may be in a different timezone, e.g., UTC. Appropriate adjustments will be made to account
+    for this.
 
   * Harvest start date/end date allow you to limit the export based on the
     harvest dates.

sfm/ui/forms.py

@@ -6,7 +6,7 @@
 from django.core.urlresolvers import reverse
 from django.utils import timezone
 from django.core.exceptions import ValidationError
-from django.utils.safestring import mark_safe
+from django.conf import settings
 
 from crispy_forms.helper import FormHelper
 from crispy_forms.layout import Layout, Fieldset, Button, Submit, Div, HTML
@@ -971,6 +971,9 @@ def __init__(self, *args, **kwargs):
                     HTML("""<h4>Limit by item date range</h4>"""),
                     'item_date_start',
                     'item_date_end',
+                    HTML("""<p class="help-block">The timezone for dates entered here are {}. Adjustments will be 
+                    made to match the time zone of the items. For example, dates in 
+                    tweets are UTC.</p>""".format(settings.TIME_ZONE)),
                     css_class="panel panel-default panel-body"),
                 Div(
                     HTML("""<h4>Limit by harvest date range</h4>"""),