Updated:

1. Permanent night vision

/effect give @s night_vision infinite 0 true

infinite needs Java 1.19.4+; the final true hides particles. On Bedrock use:

/effect @s night_vision 99999 0 true

Short durations make the screen flicker in the last ten seconds.

2. Everyone

/effect give @a night_vision infinite 0 true

Players who join later do not get it, so a repeating command block can keep applying it.

3. Always day

/time set day
/gamerule advance_time false

Use doDaylightCycle on 1.21.10 and earlier, and dodaylightcycle on Bedrock. See the time command.

4. Invisible light blocks (Java)

/give @p light 64

Light blocks are only visible while you hold one. They light builds without torches and stop mob spawns. Right click to change the level from 0 to 15.

5. Clear night vision or darkness

/effect clear @s night_vision
/effect clear @s darkness

The dark pulses near a warden are the darkness effect, which comes back while it is nearby.

6. Night vision potion

/give @p potion[potion_contents={potion:"minecraft:long_night_vision"}]

An 8 minute potion (Java 1.20.5+). On Bedrock use /give @p potion 1 6.

Troubleshooting

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