The correct answer is Set time automatically. In Windows this toggle is found under Settings → Time & Language → Date & Time, and it controls whether the operating system keeps its clock in sync with an internet time server (such as time.windows.com) using the Network Time Protocol.

The logic is straightforward: while Set time automatically is ON, Windows itself manages the clock, so the manual 'Change date and time' button is greyed out and cannot be used. To enter the date and time by hand, this option must first be turned OFF (disabled), which unlocks the manual controls.

The other options do not affect manual time entry:

• Set time zone globally / Set time zone automatically only decides which zone offset is applied; it does not lock the ability to type in the clock value.
• Night Light is purely a display feature that reduces blue light in the evening and has nothing to do with the clock.
• Enable multiple clocks just adds extra clocks for other time zones to the taskbar, again unrelated to setting the local date and time.

Hence only Set time automatically needs to be disabled before the time can be set manually.