How do I edit or delete something I logged?

Tap it on your timeline. Its details open, where you can change the time, the title, the activity and your note, or delete it. To just take the time off, tap its tick.
Logs live on your timeline, which is part of Pro (or your free week).
How do I change a log?
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Find it on your timeline. Logged things have a tick in the circle on the right. Tap the row (not the tick).
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Its details open: the time you logged, the title, the activity, tags, the link, and your session note with how it went.

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Change what you need:
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The time. Tap the pencil next to the time at the top. Set the hours, minutes and seconds, then tap Save.

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The title. Tap it and type.
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The activity. Tap the activity chip to pick another, or the x to clear it.
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The note. Tap the diary page ("Tap the page to write") and write about the session.
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When it happened. Under When? at the bottom.
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Tap Save changes at the bottom. (It says No changes until you change something.)

Want to move it to another time of day? On the timeline, drag it to the new spot. On a phone, hold it for a moment first, then drag. I ask "Move this log?" because its logged times will change to match. Tap Move, or Keep to leave it.
How do I take the time off but keep the task?
Tap the tick on the right of the row. I ask "Delete this log?": "Your logged time for this item will be removed." Tap Delete. The task stays on your timeline, unticked, so you can tick it again later.

How do I delete it completely?
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Tap the row to open its details.
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Tap the bin at the bottom left.
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I ask "Delete this entry?". Tap Delete (or Keep editing if you changed your mind).

That takes the task and its logged time off your timeline.
Can I edit old sessions from my history?
Yes. On Growth, tap View history, then tap a session. Edit and Delete are right there. See How do I look back at old sessions and revisit one?.

Good to know
- Deleting a log is for good. There's no undo and it doesn't go to Recently deleted (that's only for your library and toolkit). That's why I always ask first. See How do I bring back something I deleted?.
- A session that's still running? Deleting it from its details throws the session away ("Discard active session?"). To keep the time, stop it instead.
- Stacked items. When the same thing is stacked a few times in a row, tap the number to fan them out and edit them one by one.
- Repeating tasks. Changing or deleting a repeating task asks whether you mean just today or every day.