Library (Singleton Class) to get UpTime of your Arduino- or ESP- compatible device. Function getUpTimeSec() returns up-time in seconds as uint32_t type, does not overfloat as fast as millis(). Also has function millis64() which returns up-time im milliseconds (as millis()), but as uint64_t type, so also isn't overfloat so fast. But keep in mind 64-git operations may be significantly slower.
bobemoe/SSVLongTime
Singleton class to return UpTime in seconds. Does not overfloat as fast as millis().
C++