From what I understand, if you water at the wrong time you could promote mold growth.

When watering you want to make sure the soil is well moistened. This can be time consuming, but it is better to water thoroughly once a week than to give your garden a brief shower every day. Never use a spray nozzle on a hose, it delivers either too strong a flow or an inefficient mist. The best way of controlling water flow is to use your thumb. Always try to water the base of the plants, but in times of meager rainfall you can give the foliage an occasional spray as well. The best time to water is in the morning, but the warnings against mid-day watering are over done. Late evening is probably the worst time to water, as it leaves the foliage damp at night when molds and fungi are most active. But never let a bone-dry garden go without watering simply because you can't do it at the optimum time of day.

It's best to water at night - before dusk. You should never water during the hottest time of the day.

P.S. You will get many answers from people that have NO Clue! So Look at it from logic.
My reference is one of the answers someone gave you.

..............Rule of Thumb am................
Always have it watered before 10:00 am.
That way the hot sun doesn't make it evaporate as quick and you garden get's it's much needed drink.
.................Rule of Thumb p.m................
Your plants feet/roots sit in the water too long causing too many possible negatives to the plants.

early moring or late after noon, not when the sun shine on the plants, dont worry about mold, it rains too right..