Posted about 8 years ago. Visible to the public. Repeats.

Test if two date ranges overlap in Ruby or Rails

A check if two date or time ranges A and B overlap needs to cover a lot of cases:

1. A partially overlaps B

2. A surrounds B

3. B surrounds A

4. A occurs entirely after B

5. B occurs entirely after A

This means you actually have to check that:

  • neither does A occur entirely after B (meaning A.start > B.end)
  • nor does B occur entirely after A (meaning B.start > A.end)

Flipping this, A and B overlap iff A.start <= B.end && B.start <= A.end

The code below shows how to implement this in Ruby on Rails. The example is a class Interval, which has two attributes #start_date and #end_date. These dates are considered inclusive, meaning that if one interval ends on the day another interval starts, we consider those two intervals overlapping.

Note how we implemented both a version for loaded Ruby objects (Interval#overlaps?) and a scope that returns all overlapping intervals (Interval.overlapping). Depending on your problem you might need one or both or those.

class Interval < ActiveRecord::Base validates_presence_of :start_date, :end_date # Check if a given interval overlaps this interval def overlaps?(other) start_date <= other.end_date && other.start_date <= end_date end # Return a scope for all interval overlapping the given interval, excluding the given interval itself scope :overlapping, -> { |interval| where("id <> ? AND start_date <= ? AND ? <= end_date",, interval.end_date, interval.start_date) } end

This assumes that start_date <= end_date is always true.

Mixing dates and times

If you mix dates and times incomparisons, mind to not compare datetimes with date ranges in MySQL.


1. ------- ------- AAA AAA BBB BBB ------- ------- 2. ------- AAA B ------- 3. ------- A BBB ------- 4. ------- AAA BBB ------- 5. ------- AAA BBB ------

Does your version of Ruby on Rails still receive security updates?
Rails LTS provides security patches for old versions of Ruby on Rails (3.2 and 2.3).

Owner of this card:

Henning Koch
Last edit:
10 months ago
by Emanuel De
time, activerecord, start_time, end_time
About this deck:
We are makandra and do test-driven, agile Ruby on Rails software development.
License for source code
Posted by Henning Koch to makandra dev
This website uses cookies to improve usability and analyze traffic.
Accept or learn more