Add input parameter to GetTimeString() for external time sources

The GetTimeString() function currently calculates adjusted time using only the server's current time as its reference point, with no option to supply a different starting time value. This limits its usefulness for calculations that depend on time values from other sources, such as a device's local clock. This enhancement would add an optional input parameter allowing a specific time value to be passed into the function, with the adjusted time string returned based on that supplied value rather than the server clock. This would give customers the flexibility to perform accurate time calculations using device time or other external time sources, expanding the function's applicability beyond server-time-only scenarios.