Returns true if a date variable is before another date. That second date can be the name of another variable or a literal date string.
start_date: January 17 2015
end_date: December 1 2015
{{ if end_date | is_before:start_date }}
{{ if start_date | is_before:2014 }}
{{ if start_date | is_before:end_date }}
false
false
true