The risk is always there. Say you schedule it at 8 in the morning? Then you might interrupt the people who come in earlier. Schedule it before or after lunch? Unfortunately people eat lunch at different times too. Schedule it at the end of the day? Then the daily standup loses it's effectiveness (while you risk interrupting people who flow later in the day).

There is never such a time, if you allow any kind of flexibility or self-direction in scheduling. Moreover, if you are customer-driven, you will wind up with having calls here, there, and everywhere, that some subset of your people will be on that clash with any potential standup time.