Where is the date on a US 1 dollar silver certificate?

It depends on when the bill was printed. Before bills were standardized in 1928, dates could be just about anywhere on the front so finding them is pretty much a matter of searching the design. In many cases the dates were shown in very tiny type so finding them can be challenging.

For bills dated 1928 and later, the date position is at the bottom right of the bill, at roughly the 5:00 position with respect to the oval frame around Washington's portrait. The date should be preceded by either "SERIES" or "SERIES OF"; in addition it may or may not have a small letter corresponding to the signature combination (Treasury Secretary + U.S. Treasurer).