Second week paternity leave for fathers of Singapore children born AFTER 1 January 2017

Compulsory attendance at a national primary school for a child born AFTER 1 January 1996

The weekly rest day requirements will apply to Work Permits issued or renewed FROM 1 January 2013

Compulsory CareShield Life to start for residents born in 1980 and AFTER

Imagine : Tobacco Free Generation for those born ON AND AFTER 1 January 2010

Using a starting, date-based approach is conventional policy making principle. This is called Grandfathering. It is widely used in many sectors for example: law, technology, science, standard compliance and sports.

Wikipedia: A grandfather clause (or grandfather policy, grandfathering, or grandfathered in) is a provision in which an old rule continues to apply to some existing situations while a new rule will apply to all future cases. Those exempt from the new rule are said to have grandfather rights or acquired rights, or to have been grandfathered in. Frequently, the exemption is limited; it may extend for a set time, or it may be lost under certain circumstances. For example, a grandfathered power plant might be exempt from new, more restrictive pollution laws, but the exception may be revoked and the new rules would apply if the plant were expanded. Often, such a provision is used as a compromise or out of practicality, to allow new rules to be enacted without upsetting a well-established logistical or political situation. This extends the idea of a rule not being retroactively applied. https://en.wikipedia.org/wiki/Grandfather_clause