Well, just use the time command as described above and use an appropirate number for the desired time of day.
See
http://wiki.minetest.net/Time_of_day for a list of useful values for the time command.
If this does not answer your question, then you need to reword your question so we can understand it.
More infos about setting the time:
Since 0.4.13, the time command was extended to also accept times in the 24-hour format.
So you could just type in into the console or chat:
Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.
Instead of the harder to calculate:
Your phone or window isn't wide enough to display the code box. If it's a phone, try rotating it to landscape mode.
Alternatively, you can also set the time of day directly in the world files without having to start Minetest before. Look for the file %YOUR_MINETEST_USER_DIRECTORY%/worlds/%YOUR_WORLD_NAME%/env_meta.txt (Replace the weird “%%” names with the directories approprieate to your system). Edit the number on the line which says “time_of_day” and use a value between 0 and 24000 (same format as for /time, but 24-hour format is not supported).