Where it sits on the calendar
A fictional indie feature's production calendar might look like this:
| Phase | Dates | Length |
|---|---|---|
| Pre-production (prep) | Aug 17 to Sep 28 | 6 weeks |
| Rehearsal | Sep 24 to 25 | 2 days, inside the last prep week |
| Principal photography | Sep 29 to Oct 22 | 18 shoot days, Monday to Friday |
| Wrap period | Oct 23 to Oct 30 | 1 week |
| Post-production | Nov 2 onward |
Day 1 of principal is the first shoot day with the main unit. The last day is picture wrap. Days with only second unit before day 1 are usually labeled separately so they don't change the start date that contracts reference.
Why the date is contractual
A lot of paperwork hangs on "commencement of principal photography." Pay-or-play clauses with cast often become binding around that date. Financing agreements and completion bonds set milestones against it. Insurance policies start coverage before it. Under the DGA Basic Agreement, the employer must disclose to the director, before the start of principal photography, what material is intended for second unit (DGA Article 7).
That's why a producer who pushes the start by a week sends notices to cast agents, the bond company, and the insurance broker.
What doesn't count
Additional photography after picture wrap, including pickup days and reshoots, is tracked separately. SAG-AFTRA's theatrical consecutive employment rules allow producers to recall performers after principal photography ends for retakes, added scenes, and similar work without paying the gap (SAG-AFTRA). Test shoots and camera tests during prep aren't principal either.
Common confusions
Film students often call the whole project "production". On a union show, crew deal memos may have separate prep, shoot, and wrap rates, so being clear about which days are principal affects pay.
Another confusion is between the scheduled number of shoot days and the calendar length. In the example above, 18 shoot days with weekends off take 24 calendar days. Budget crew and equipment by weeks, and use the shoot days estimator to size the day count first. The phase before it is pre-production.