Your question is about application time for Latisse. Truth is, the application for this particular agent, and a lot of medications in general, is not that time-sensitive.
Certain medications, for example birth control pills, are suggested to be taken around the same time every day. However, if you were to take it at 9 p.m. versus 11 p.m., there won’t be much difference in terms of overall efficacy.
Similarly, with topical medications, the time of application is not usually relevant for best efficacy. I would say when you best remember to apply, whether that's 6 p.m. or 9 p.m., is when you should apply Latisse.