（當）…的時候grammar point · tier 2 · temporal frame (當)…的時候 (when / while …)
Wraps a clause into a span of time and stamps the main action as happening within that span: when / while X holds, Y.
字源 FORM what the parts do
時候 names a watched stretch of time: 時 cuts the day into pieces by the sun, 候 is a man posted to watch one pass. 的 pins the clause before it onto that stretch. 當 is optional out front, aligning onto the moment (the same 當 as 當時).
故事 STORY a scene to remember it by
A window opens over a stretch of time. Whatever you do sits inside the window — not before it opens, not after it shuts.
字源記憶法
框 · Frame
（當）[clause] 的時候，[main clause]
觸 · Trigger
You want to set one event inside the span of another: while this is going on, that happens.
序 · The move
1State the situation as a full clause that names a stretch of time.Is it a span you can be inside, not a single instant?
2Close it with 的時候 and a comma; put the main action after.Does the main action fall within that span, not just at its start?
3Front 當 only for weight or formality; drop it in plain speech.Does it still read cleanly with 當 removed?
例 · Examples
1他生氣be angry的時候during the time (when)，最好had best不要跟他開玩笑crack a joke。
…的時候 marks the whole span — the action sits anywhere inside it. 一…就… marks the instant the span opens — the action fires the moment X happens. Window vs. trigger.