I have to merge a queenless hive, does time of day matter to maximize the amount of bees I can save? The go to hive is right next to the weak hive. Late afternoon? Morning? No difference?
If you wan't to save bees, I would do it in the evening if you wan't to save as many as you can. Leave your strong hive where it is, and place your weak hive on top.
If you moved your strong hive to your weak hive, you risk losing more bees.
Poke a couple small holes in the paper and that will help the process move along.
If your queened hive is next door, mid day would be fine. The returning foragers from the weak hive will mill around till they find the hive next to it. As long as they have something to offer they'll be accepted.
What I do to combine is take a bottom board (upside down) and set it on top of the box to be combined to give the ones that are milling around a place to go. Slip in a entrance reducer after things have settled down.