Time/CPU Cycles
Intel/AMD have an inst that returns the num of CPU cycles since boot.  This is 
not a steady, calibrated real time value.  TempleOS measures it and you can 
convert with cnts.time_stamp_freq, a value continuously calibrated from other 
cnts.
Busy                Funct Loosely timed.
CPURep              Funct Report number of cores and clock freq.
GetTSC              Funct _extern SYS_INITRAMFS_PTR U8* sys_initramfs_ptr;
PortNop             Funct Innoculous (reads IRQ Mask) which should take fixed time
cnts                GlbVar CCntsGlbls cnts= {1,0,2676302000,2676302,2676302000,FALSE};


                                   
Time/Date
Dates are 32-bit signed ints representing the number of days since the birth of 
Christ.  Negative values represent B.C.E. dates.

DayOfWeek           Funct Day of week, given 32-bit day since AD 0.
FirstDayOfMon       Funct First day of month, given 32-bit day since AD 0.
FirstDayOfYear      Funct First day of year, given 32-bit day since AD 0.
LastDayOfMon        Funct Last day of month, given 32-bit day since AD 0.
LastDayOfYear       Funct Last day of year, given 32-bit day since AD 0.
YearStartDate       Funct 32-bit day since AD 0, given year number.
mon_start_days1     GlbVar U16 mon_start_days1[12]=
mon_start_days2     GlbVar U16 mon_start_days2[12]=


                                
Time/Date/CDate
TempleOS uses a 64-bit value, CDate, for date/time.  The upper 32-bits are the 
days since Christ.  The lower 32-bits store time of day divided by 4 billion 
which works out to 49710ths of a second.  You can subtract two CDate's to get a 
time span.

Use CDATE_FREQ to convert.

Date2Struct         Funct Cvt CDate to CDateStruct.
Now                 Funct Current datetime.
Struct2Date         Funct Cvt CDateStruct to CDate.
local_time_offset   GlbVar CDate local_time_offset;


                                  
Time/Jiffies
One jiffy is one time slice.  cnts.jiffies returns time slices since boot.

SysTimerRead reads the timer ticks since boot.  It's not as fast as GetTSC.

Use JIFFY_FREQ to convert cnts.jiffies.

Use SYS_TIMER_FREQ to convert SysTimerRead.

Sleep               Funct Not for power-saving. It is to make a program pause without hogging the CPU.
SleepUntil          Funct Not for power-saving. It is to make a program pause without hogging the CPU.
SysTimerRead        Funct System timer count with overflow already handled.
cnts                GlbVar CCntsGlbls cnts= {1,0,2676302000,2676302,2676302000,FALSE};


                                  
Time/Seconds
Beat                Funct Time in music beats.
tM                  Funct Time in seconds synced to music subsystem.
tS                  Funct Time since boot in seconds as a float.