Generate random datetimes in rails with the minutes belongs to range(00, 30) - ruby-on-rails

Question

Event model which has start and end datetime attributes in the database. I want to seed some random events but the event time should be proper.
For example:
6.times { date_range << DateTime.now + (rand * 21) }
generates
[Thu, 03 Aug 2017 21:22:48 +0530,
Tue, 08 Aug 2017 17:36:29 +0530,
Sat, 29 Jul 2017 06:19:51 +0530,
Sat, 29 Jul 2017 13:36:21 +0530,
Thu, 27 Jul 2017 15:08:55 +0530,
Fri, 04 Aug 2017 13:53:03 +0530]
which is the correct behaviour.
But how to generate random datetime like this:
[Thu, 03 Aug 2017 21:00:00 +0530,
Tue, 08 Aug 2017 17:30:00 +0530,
Sat, 29 Jul 2017 06:00:00 +0530,
Sat, 29 Jul 2017 13:00:00 +0530,
Thu, 27 Jul 2017 15:30:00 +0530,
Fri, 04 Aug 2017 13:00:00 +0530]
So in order to display these events properly on a calendar.

Answer 1

Could try separating out each segment and adding them onto the date individually
date_range = 6.times.collect do
DateTime.now.beginning_of_day + # starting from today
rand(21).days + # pick a random day, no further than 3 weeks out
rand(24).hours + # move forward to a random hour on that day
(rand(2) * 30).minutes # and then decide whether to add 30 minutes
end
or, could combine the hours + minutes
date_range = 6.times.collect do
DateTime.now.beginning_of_day + # starting from today
rand(21).days + # pick a random day, no further than 3 weeks out
(rand(48) * 30).minutes # pick a random interval of 30 minutes to add in
end

Answer 2

Found the working solution but not complete:
6.times { date_range << DateTime.parse((DateTime.now + (rand * 21)).beginning_of_hour.to_s) }
[Mon, 31 Jul 2017 06:00:00 +0530,
Thu, 03 Aug 2017 15:00:00 +0530,
Fri, 11 Aug 2017 14:00:00 +0530,
Mon, 31 Jul 2017 09:00:00 +0530,
Wed, 09 Aug 2017 16:00:00 +0530,
Sat, 12 Aug 2017 13:00:00 +0530]
This can work for now but need some datetime with 30 minutes as well.