Options on Omni are European-style, meaning the buyer can only exercise the option on the expiration date. You can trade (close) out of a position anytime before expiration. Options expire at 4pm ET on the expiration date.
When can I submit exercise instructions?
The option buyer has until 5pm on expiration to submit exercise instructions. The buyer can save and edit instructions any time up until 5pm. If sufficient collateral is not on deposit at LedgerX, the exercise instructions will not be accepted. There is no auto-exercise.