The effective date is the date your insurance coverage commences. In most cases, this will always be the first of a future month, although a newborn baby or newly adopted child can have coverage retroactive to the date of birth or adoption.
Here’s more about how effective dates work when you enroll in a health plan through the exchange.
In most cases, employer-sponsored coverage will be effective the first of the month following your enrollment, or the first of the coming plan year if you enroll or make a plan change during your employer’s open enrollment period.