For OSPi, you will NOT see NTP option because time is managed by your RPi, the firmware does not manage time directly. So if you get a wrong time, you should check your RPi settings, there you can change NTP server etc.
For microcontroller-based OpenSprinkler, the firmware allows you to choose which NTP server you want to use. Since firmware 2.1.9(4) the default is 0.0.0.0, which tells the firmware to use pool.ntp.org. Otherwise if you put in a custom server IP, then it uses that IP.