Yes and depends on your coding abilities. Blynk is a GUI interface with some built in GPIO control and IoT preferences, you still need to use code for more complete control than simply toggling GPIO pins.
Depending on your RTC, there may be ways of changing it’s settings on the fly. Google for that, and once you know how, then you can feed the required info in the required format (String? Numerical?) from a widget of some sort… Terminal, Text input or possibly even the Time Input Widget… then your code would transfer that input to the RTC.