All day event icalendar gem - ruby-on-rails

Question

I am using the below to setup an event to export to ical with the icalendar gem.
#calendar = Icalendar::Calendar.new
event = Icalendar::Event.new
event.dtstart = ev.start_at.strftime("%Y%m%d")
event.dtend = ev.end_at.strftime("%Y%m%d")
event.summary = ev.summary
#calendar.add
In order to make an event all day it needs to look like this:
DTSTART;VALUE=DATE:20101117
DTEND;VALUE=DATE:20101119
Right now I am using
event.dtstart = "$VALUE=DATE:"+ev.start_at.strftime("%Y%m%d")"
This will output
DTSTART:$VALUE=DATE:20101117
and then I replace all ":$" with ";" with
#allday = #calendar.to_ical.gsub(":$", ";")
Is there a more direct way to save dates as all day?

Answer 1

I played around with this and figured out one way. You can assign properties to the event dates, in the form of key-value pairs. so you could assign the VALUE property like so:
event = Icalendar::Event.new
event.dtstart = Date.new(2010,12,1)
event.dtstart.ical_params = { "VALUE" => "DATE" }
puts event.to_ical
# output
BEGIN:VEVENT
DTSTAMP:20101201T230134
DTSTART;VALUE=DATE:20101201
SEQUENCE:0
UID:2010-12-01T23:01:34-08:00_923426206#ubuntu
END:VEVENT
Now the fun part. Given a calendar you can create an event and pass in a block which initializes the date with its properties:
calendar.event do
dtstart Date.new(2010,11,17), ical_params = {"VALUE"=>"DATE"}
dtend Date.new(2010,11,19), ical_params = {"VALUE"=>"DATE"}
end

Answer 2

So this thread seems quite old (and did not solve the problem with the most recent version of the icalendar gem - 2.3.0). I've recently had to create "all day" calendar events in ics format. I've found this to be a much better solution (and seems to work the way you'd expect calendars to handle it) - see the snippet below
date = Date.new(2010,11,17)
event = Icalendar::Event.new
event.dtstart = Icalendar::Values::Date.new date
event.dtstart.ical_param "VALUE", "DATE"
event.dtend = Icalendar::Values::Date.new (date + 1.day)
event.dtend.ical_param "VALUE", "DATE"
puts event.to_ical
The above code produces the following output:
BEGIN:VEVENT
DTSTAMP:20150521T162712Z
UID:4c239930-15ba-44b4-a045-c6fae3d858d2
DTSTART;VALUE=DATE:20101117
DTEND;VALUE=DATE:20101118
END:VEVENT
Note that the Date does not have a time associated with it. The code in the prior reply currently produces the time. I had to dig into the source code for icalendar to figure out this solution.
I hope this helps someone else.
Cheers!