Yes, the F-series PLCs incorporate a real-time clock with a battery backup built in.
The M-series PLCs also incorporate a real-time clock. However, the clock is shutdown when all power to the PLC is turned off. If there is need for a real-time clock to keep running even when power is off, an optional MX-RTC battery backed real time clock module can be purchased from TRi ( this is mounted between the 28pin SRAM and the 28pin socket on any of the M-series PLCs).
To optimize the computational performance, the current generation of F-series and M-series PLCs only compute using 32-bit integer arithmetic but they do not support floating point computation.
However, many computational task that seems to involve floating point math can also be handled using "fixed point" math, in which case a unit integer represents, say 0.01, and since a 32-bit integer can represent numbers of up to +/- 2 billion you can get a lot of fractional arithmetics computation done this way. You can still display a fixed point data on LCD display with decimal places using TBASIC divide and modulo operator. Please read more at: http://www.tri-plc.com/yabbse/index.php?board=2;action=display;threadid=1084