From and to work together in English. From X identifies the start, and to X identifies the end.
We will work from 8am to 5pm.
One meaning of to X is identifying motion destination/where a motion ends. Work is moving starting from 8am and ending when 5pm occurs.
If the from X part is already known or understood, it can be omitted.
We will work to 5pm. (We already are at work or know when we start).
Now if you use at:
Tickets are available at the end of the month.
that will mean that tickets are available when the end of the month happens, not from now to the end of the month.