Here is an example model of how you can connect a Global Table to a Sourcen's arrival schedule:
sourceschedule-datetimeformat-example-v16-1-2.fsm
GlobalTable1 is set up with the time/date format I want to use in the Source. To use the convert() command, the format needs to be exactly what you see here.
In the Source's OnReset trigger, I used code to reference those times/dates in the Global Table, convert them into model time using the convert() command, then copy that number into the Source's Arrivals Table. I was able to use a command called getvarnode() to get a reference to the arrival table - it is a variable in the Source's tree called schedule. Since this variable is a table itself, I used the settablenum() command to make the changes.
To change the Model Start Time with code in the OnModelReset trigger, you'd need to do something like:
treenode startNode = node("/Tools/ModelUnits/ModelDateTime/start", model());
double startTime = convert("8:00:00 AM Fri 26 Aug 2016", DATETIME_STR, FS_DATETIME);
set(startNode, startTime);
applicationcommand("convertunixtime", startNode, startTime);
Where the first parameter in the convert() command (the string with the time and date) is the value that you want to change the model's start time to. That string is getting converted into a format called FlexSim datetime, which is a number that is needed in the application command called convertunixtime. So if you are starting with a different format, it needs to be converted into the FlexSim datetime format before being used in the convertunixtime application command.