Setting DateTimes can be a difficult or ugly thing, especially through a web form. Finding a good DatePicker or TimePicker is easy, but getting them to work on both can be difficult. TimeSplitter automatically generates accessors for date, time, hour, and min on your datetime or time attributes, making it trivial to use different form inputs to set different parts of a datetime field.

This gem is based on SplitDatetime by Michi Huber. TimeSplitter improves on the gem, updating for Rails 4, adding time accessors, and providing a safer and more consistent default setting.

$ gem install time_splitter

In your Gemfile:

gem "time_splitter"

After bundling, assuming you have an Event model with a starts_at attribute, add this to your model:

class Event < ActiveRecord::Base
  extend TimeSplitter::Accessors
  split_accessor :starts_at
end

In your view:

<%= simple_form_for @event do |f| %>
  <%= f.input :starts_at_date, as: :string, input_html: { class: 'datepicker' } %>
  <%= f.input :starts_at_hour, collection: 0..24 %>
  <%= f.input :starts_at_min, collection: [0, 15, 30, 45] %>
  <%= f.input :starts_at_time, as: :time
  <%= ... %>
<% end %>

Add your js datepicker and you're good to go. (Of course, this also works with standard Rails form helpers).

If you are using Rails < 4.0 and/or are not using StrongParameters, you must add attr_accessible for any of the split attributes you want to permit mass-assignment. TimeSplitter provides the methods that can be directly accessed, but will not automatically whitelist any of them for mass-assignment.

By default, the read accessors provided by TimeSplitter are as follows:

starts_at_date #=> Date
starts_at_time #=> Time or Timey class used in :default option
starts_at_hour #=> Fixnum
starts_at_min  #=> Fixnum

You can override the default read format for date and time if you so choose, though doing so may not work well with certain form input types.

split_accessor :starts_at, date_format: "%D", time_format: "%I:%M%p"

starts_at_date #=> String "2013-10-13"
starts_at_time #=> String "01:44PM"

See Time#strftime for formats.

You can specify multiple datetime fields to split:

split_accessor :starts_at, :ends_at, :expires_at, format: "%D"

You can specify a default timey object to write. If starts_at is nil, which it would be at the time of a new or create call, TimeSplitter will use the default value as the basepoint for modification.

split_accessor :starts_at, default: -> { DateTime.current }

# model = Model.new(starts_at_time: '09:00')
# model.starts_at
# => Thu, 10 Oct 2013 09:00:00 -0400 # DateTime

The default time object is Time.new(0, 1, 1, 0, 0, 0, '+00:00').

Note that TimeSplitter does not handle seconds at this time, and from testing it appears they are set to zero when modifying them.