During a hail, rain, sleet, snow or storm event is the worst time to prune a tree. Trees tend to recover when proper pruning schedules are not followed since they must be pruned when pruning never has been done, when there is danger to the environment or to the tree or when the tree suffers from damage, death, decay or disease. Pruning during human-imposed or natural moisture events will increase the possibility of terminal cankers from cuts into wet wood and, in the case of lightning and proximity to power sources, the probability of animal and human casualties.
winter
Your English is incorrect, should read, "How do you prune an olive tree?"
early spring and late summer
The best time to prune an Olive Tree is soon after the fruit has been harvested when the tree is in a more dormant state. Here in Spain many trees are pruned at the same time as the fruit is being picked often with branches cut then shaken for the Olives.
You can prune it but the symmetrical shape that makes it attractive will be wrecked. If you do prune only tip prune.
early spring and early autum
If you wanted to prune a tree, you will need a Class 1 fulcrum.
I would guess that the best time to prune the tree would be after any chance of frost is over, but before the tree blooms. Otherwise, you risk cutting off the young fruit and will have year of few or no grapefruit. Most citrus matures in November-December.
prune them
The best time to replant a silk tree would be in late February or early March. You can prune the tree a few months before the move.
As close to the winter season as possible. The tree must be dormant. Do not prune more than 25% of the overall tree. Keep cuts 1/4" out from the shoulder (black ring) at the trunk. Prune branches that grow up and tangle. Remove all dead wood. Never prune this tree during its growing season.
in the dead of winter when growth is most impeded.