What are subscription anchor dates?
Anchor dates are an optional add-on to Subscription Programs that set a day on which billing interval calculations should be made + schedule specific product ship dates.
The most common use-case for anchor dates is when a shop wants to release subscription boxes on a specific day. For example, say a shop releases seasonal subscription drop: ‘Autumn’ product on October 1st, etc. These dates are always fixed regardless of when the previous subscription product was delivered.

Adding an Anchor

When managing a Subscription Program, you will see an option to add an Anchor. Note—this option will not populate if your billing interval is set to "Days".
You can select your anchor day to be a specific Week Day (ex. Monday), Month Day (ex. 15th), or Year Day (ex. July 30th).
If you select a Week Day or Month Day from the dropdown, you'll also be presented with the option to add an optional Cutoff Day and determine subscription behavior Pre-Anchor:

Cutoff Days

A cutoff day is how many days in advance of the delivery anchor the order would need to be placed in order to qualify for the next delivery cycle.

Pre-Anchor Behaviors

Pre-Anchor Behavior is the possible fulfillment of the first order when placed within the cutoff. ASAP means orders placed inside a cutoff can be fulfilled or delivered by the next anchor. NEXT means orders placed inside a cutoff can be fulfilled or delivered at the following anchor.