This site has that function. When you go to the database main page, any state that is highlighted in green has updated in the past 24 hours, any in yellow, the past 7 days. If you "drill down" into a state, that same color coding is applied to each county. If you drill down into a county, that is applied to individual channels (or trunked systems then channels).
Sentinel does not consume any date stamp on the received data, so has no way of knowing what channels are new, changed, or deleted.