Question

How do I calculate the difference of two dates in months? Also, incase it makes a difference, I am working with Date objects, not DateTime. Also, some rounding options might be nice so I can control if I want to round up or down on partial months.

Thanks!

Answer 1

Subtracting one Date or DateTime from another will yield the number of days as a fraction, but this can be evaluated as a Float or Fixnum as required.

For instance:

(Date.today - Date.today.advance(:months => -3)).to_f
# => 89.0

There were 89.0 days between today and the same calendar date three months ago. If you work this using 30-day months, or 30.4375 as they are on average, you end up with 2.92 months elapsed between then and now, or rounded up to the nearest integer, 3.

If you want to compute the precise number of calendar months, that is trickier, but can be done.