Does this account for daylight saving transitions in the cutoff time itself?

The cutoff is treated as a fixed local wall clock time in the stated zone, so it applies the same way on either side of a transition, since a wall clock cutoff time like 17:00 always means 17:00 local time regardless of the date.

Can the cutoff time be midnight?

Yes, a midnight cutoff effectively means any submission after 00:00:00 on a given date always rolls to the next open day, since no time that day can be before midnight.

Cutoff-Time Deadline Planner

Decide whether a submission counts for the same open day or rolls to the next open day, based on a stated local cutoff time and business calendar. The submitted time is treated as already local to your stated time zone.

Need to chain a cutoff rule with several other date rules in order? See Date Rule Chain Planner.

Worked example

A submission on a Friday at 18:00, with a 17:00 cutoff and a Monday through Friday open schedule, arrives after that day's cutoff, so it rolls forward to the next open day, the following Monday, skipping the closed Saturday and Sunday in between. The same submission arriving at 16:00 on that same Friday, before the cutoff, counts for Friday itself since it is both an open day and before the stated cutoff time. A submission arriving at any time on a Saturday never counts for that day at all, since Saturday is not an open day in this schedule, regardless of what the cutoff time says.

Common mistakes

Checking only the cutoff time and forgetting to check whether the submission date is even an open day in the first place. Both conditions have to hold for a same-day result.
Assuming the effective date always advances by exactly one calendar day. It advances to the next open day, which can be several calendar days later across a weekend or holiday closure.

Limitations

This applies the exact cutoff time and open schedule entered. It makes no guarantee about shipping carriers, banking settlement, or any other real-world process that may use its own separate cutoff rules beyond what you have stated here.

Frequently asked questions

Does this account for daylight saving transitions in the cutoff time itself?: The cutoff is treated as a fixed local wall clock time in the stated zone, so it applies the same way on either side of a transition, since a wall clock cutoff time like 17:00 always means 17:00 local time regardless of the date.
Can the cutoff time be midnight?: Yes, a midnight cutoff effectively means any submission after 00:00:00 on a given date always rolls to the next open day, since no time that day can be before midnight.