Can you cast a sorcery during your opponent's turn if you have flash?

Normally, sorceries can only be cast during your own main phase when the stack is empty and you have priority — this is the 'sorcery speed' restriction defined in CR 307.1.

However, flash overrides this restriction. CR 702.8a states that flash allows a player to cast that spell 'any time they could cast an instant.' Instants can be cast at any time you have priority (CR 304.1 and 116.1), including during your opponent's turn, during combat, or in response to other spells or abilities.

The flash ability can come from the card itself (e.g., a sorcery printed with flash) or from an external effect that grants flash to spells you cast, such as Teferi, Mage of Zhalfir or Vedalken Orrery. Either way, the result is the same: sorcery-speed restrictions are bypassed.

Example: Your opponent attacks you and moves to their combat damage step. You control a Vedalken Orrery, which gives all your spells flash. You may cast a sorcery like Day of Judgment during this combat damage step, because Orrery grants it flash, letting you cast it as though it were an instant.

Note: Flash only changes when you can cast the spell. All other rules — paying costs, targeting, etc. — still apply normally (CR 702.8a).