Effective dates can be tricky so let's review!
If a dependant was active before the Plan start date, their effective date will be the first day of the Plan. For example, if you had a kid in 2015, but the Plan was effective 2024-09-01, their effective date would be 2024-09-01.
If the dependant was active after the first day of the plan (let's say you got married on 2024-09-15 but the Plan was active 2024-09-01) their effective date would be 2024-09-15.
Common-law partners are eligible after 12 months of co-habitation. If your common-law status predates the Plan start, their effective date will be 2024-09-01, if you hit the 12-month co-habitation marker after 2024-09-01, use the date you hit the 12 month mark 🙂