This template is used on the London transport Portal with {{Random subpage}} to force a particular biography to appear on a relevant anniversary date instead of a random biography. If no relevant anniversary date is in the list within the template, the switch will allow {{Random subpage}} to operate normally.
The only parameter is the default to be used when a date match is not made:

Example:
{{Random subpage|page=Portal:London transport/Selected biographies|start={{LTP anni switch|1}} |end={{LTP anni switch|15}} |seed=5}}