advance

Provides precise Date calculations for years, months, and days. The options parameter takes a hash with any of these keys: :years, :months, :weeks, :days.

The increments are applied in order of time units from largest to smallest. In other words, the date is incremented first by :years, then by :months, then by :weeks, then by :days. This order can affect the result around the end of a month. For example, incrementing first by months then by days:

Date.new(2004, 9, 30).advance(months: 1, days: 1)
# => Sun, 31 Oct 2004

Whereas incrementing first by days then by months yields a different result:

Date.new(2004, 9, 30).advance(days: 1).advance(months: 1)
# => Mon, 01 Nov 2004