Subtract n hours from a DateTime in Ruby

Question

I have a Ruby DateTime which gets filled from a form. Additionally I have n hours from the form as well. I\'d like to subtract those n hours from the previous DateTime. (To

Answer 1

If you are working in Rails, the following super-intutive possibility exists:

> Time.now - 12.hours
=> 2019-08-19 05:50:43 +0200

(This also works with seconds, minutes, days, and years)

if you're using just Ruby, DateTime can't do this, but Time can:

t = Time.now
t = t - (hours*60**2)

Note that Time also stores date information, it's all a little strange.

If you have to work with DateTime

DateTime.commercial(date.year,date.month,date.day,date.hour-x,date.minute,date.second)

might work, but is ugly. The doc says DateTime is immutable, so I'm not even sure about - and <<