Good morning @Alex_Bijmolt,
I'm currently working on processing the return values of AT commands as well. I only want my code to continue if "OK" is returned. The MODEM_STREAM.read() returns a decimal value which can be converted to ASCII. Saving the MODEM_STREAM.read() in a char did the job for me. After that you can do whatever you want with the char. For example look at index numbers to determine hours, minutes, seconds etc..
char answer = MODEM_STREAM.read();