Time follows the same boundary as cost. A small release with a known job can be planned in weeks. A product that still has four undecided audiences will spend those weeks in meetings.
Count discovery, design of the critical journeys, build, device testing, and store review. Leave room for the first fixes. A date that ignores review is a launch announcement, not a plan.
If the business needs to learn something by a particular month, cut the release until that date can hold the learning. Do not keep the feature list and hope the calendar stretches.