The arithmetic

Nth-weekday rule

Technical our rule type for holidays pinned to a weekday

The third Monday in January — a holiday pinned to a weekday rather than a date.


Often confused with fixed-date rule substitution

An nth-weekday rule fixes an observance to a weekday position rather than a date: the third Monday in January, the second Monday in October, the last Monday in May.

The point of the design is that such a holiday can never fall on a weekend, so it needs no substitution rule and always produces a long weekend. Several countries have deliberately converted fixed-date holidays into this form for exactly that reason — Japan's Happy Monday legislation and the United States' Uniform Monday Holiday Act both did it.

The variant is a rule relative to an nth weekday: Botswana observes the Tuesday following the third Monday in July, which is a holiday defined by its distance from another holiday that is itself defined by a weekday position.

Three days that show it

Three holidays pinned to a weekday rather than a date. None of them can fall on a weekend, which is the point of writing the rule this way.

🇯🇵 Monday 11 January 2027Japan Coming of Age DayThe second Monday in January, moved to this form by the Happy Monday legislation.
🇺🇸 Monday 18 January 2027United States Martin Luther King Jr. DayThe third Monday in January.
🇧🇼 Tuesday 20 July 2027Botswana Tuesday following President's DayOne day after the third Monday in July — a rule relative to another weekday rule.

Nth-weekday rule vs fixed-date rule

A fixed-date holiday can land on a weekend and need substitution. An nth-weekday holiday cannot, which is usually why it was written that way.

Nth-weekday rule vs substitution

Substitution moves a holiday that landed badly. An nth-weekday rule prevents the situation instead of correcting it.

See also fixed date rule · substitution · long weekend · bridge day

We hold this as rule_type: nth_weekday — 319 rules — and relative_to_nth_weekday. See what we hold.