Date-time comparison in Ruby

I have one date, let's say '2010-12-20' of a flight departure, and two times, for instance, '23:30' and '02:15'.

The problem: I need to get datetimes (yyyy-MM-dd HH:mm:ss, for example, 2010-12-17 14:38:32) of both of these dates, but I don't know the day of the second time (it can be the same day as departure, or the next one).

I am looking for the best solution in Ruby on Rails. In PHP would just use string splitting multiple times, but开发者_高级运维 I believe, that Rails as usually, has a much more elegant way.

So, here is my pseudo code, which I want to turn into Ruby:

depart_time = '23:30'
arrive_time = '02:15'
depart_date = '2010-12-20'
arrive_date = (arrive.hour < depart.hour and arrive.hour < 5) ? depart_date + 1 : depart_date
# Final results
depart = depart_date + ' ' + depart_time
arrive = arrive_date + ' ' + arrive_time

I want to find the best way to implement this in Ruby on Rails, instead of just playing with strings.

---

This is just pure Ruby, nothing to do with Rails:

require 'date'

depart_time = DateTime.strptime '23:30', '%H:%M'
arrive_time = DateTime.strptime '02:15', '%H:%M'
arrive_date = depart_date = Date.parse( '2010-12-20' )
arrive_date += 1 if arrive_time.hour < depart_time.hour and arrive_time.hour < 5

puts "#{depart_date} #{depart_time.strftime '%H:%M'}",
     "#{arrive_date} #{arrive_time.strftime '%H:%M'}"
#=> 2010-12-20 23:30
#=> 2010-12-21 02:15