I realize that this topic is over a year old but I just want to add that this thread helped debug my issue… and this is one of the top threads on Google if you google “opensprinkler ntp”. I turned on my unit (hardware 2.3-AC,firmware 2.1.9(3), iOS app version 2.2.4) this week and the time kept defaulting to Dec. 31, 1999. After a bunch of Googling and specifically this thread, I exported the settings, edited the backed up settings JSON file using Notepad, changed the ntp1, ntp2, etc. settings from “ntp1″:50,”ntp2″:297,”ntp3″:210,”ntp4”:169, to all zeroes so that it looked like this “ntp1″:0,”ntp2″:0,”ntp3″:0,”ntp4”:0, and then reimported this settings file back in and rebooted the unit and NTP sync’ing went back to working. A belated thank you for everyone who replied above.
Please either update your firmware to the latest 2.1.9(7), or change NTP to a valid NTP server. Only firmware 2.1.9(7) supports default NTP server when NTP IP is set to 0.0.0.0 — earlier firmwares do NOT support the default NTP server.