frozen_string_literal: true

Yyyymmdd

Integer calendar-day encoding (YYYYMMDD) and related compact date/time formats, extracted from a production Rails codebase.

Why

Some apps store and query calendar days as plain integers (20240714) rather than date columns. That makes range queries and grouping trivial, but needs reliable conversion and validation. This gem is that conversion + validation layer.

Install

# Gemfile
gem 'yyyymmdd', path: '/path/to/yyyymmdd' # or via rubygems once published

require 'yyyymmdd'

Usage

Date ↔ YYYYMMDD

Date.new(2024, 7, 14).yyyymmdd     # => 20240714
Date.from_yyyymmdd(20240714)       # => #<Date: 2024-07-14>
Date.from_yyyymmdd('20240714')     # => #<Date: 2024-07-14>
Date.from_yyyymmdd(nil)            # => nil

Time.utc(2024, 7, 14, 15, 30).yyyymmdd  # => 20240714

Datetime ↔ YYYYMMDDHHMMSS

Time.utc(2024, 7, 14, 15, 30, 0).yyyymmddhhmmss  # => 20240714153000
Time.from_yyyymmddhhmmss(20240714153000)

Time-of-day ↔ HHMM

Time.zone.local(2015, 5, 30, 10, 55).hhmm  # => 1055
Time.from_hhmm(1055)                       # hour/min of current day

Year-week

Date.new(2024, 7, 14).yearweek     # => 202428 (strftime %Y%W)
Date.from_yearweek(202428)

Validation

Yyyymmdd.valid?(20140101)      # => true
Yyyymmdd.valid?('020140101')   # => false (leading zero / wrong length)
Yyyymmdd.validate!(params[:d]) # raises ArgumentError when invalid

# ActiveModel
class FoodLogEntry
  include ActiveModel::Validations
  attr_accessor :yyyymmdd
  validates :yyyymmdd, yyyymmdd: true  # integer round-trip must match
end

The ActiveModel check requires the value to round-trip to the same object, so the integer 20140101 is valid and the string "20140101" is not. Param validation (Yyyymmdd.validate!) accepts either form when it is exactly 8 digits.

Helpers mixin

include Yyyymmdd::Helpers
validate_yyyymmdd!(params[:yyyymmdd])

Day-key ranges

Yyyymmdd.between(20240701, 20240703)
# => [20240701, 20240702, 20240703]

Yyyymmdd.between(20240701)  # end defaults to start + 7 days

Other helpers

Date.current.date_of_next(:monday)
Date.current.date_of_last(:sunday)
Date.current.for_datetime_column  # UTC midnight Time for datetime columns
Time.datetime_epoch               # Time.zone.local(1970, 1, 1)

Development

bundle install
bundle exec rake test

License

MIT — see LICENSE.