Epoch in Modelica

A common requirement in programs is getting the number of seconds, milliseconds, or nanoseconds since the Unix epoch. Here’s how to do it in Modelica.

model Epoch
  import Modelica.Utilities.System;
  import Modelica.Utilities.Streams;
  
equation
  when initial() then
    // Get the current time in seconds since the epoch
    Real currentTime = System.getTime();
    
    // Print the current time
    Streams.print("Current time: " + String(currentTime));
    
    // Calculate milliseconds and nanoseconds
    Real milliseconds = currentTime * 1000;
    Real nanoseconds = currentTime * 1e9;
    
    Streams.print("Seconds since epoch: " + String(currentTime));
    Streams.print("Milliseconds since epoch: " + String(milliseconds));
    Streams.print("Nanoseconds since epoch: " + String(nanoseconds));
    
    // Convert back to time
    Real convertedTime = System.getTime();
    Streams.print("Converted time: " + String(convertedTime));
  end when;
end Epoch;

In Modelica, we don’t have direct equivalents for all the time-related functions available in some other languages. However, we can use the System.getTime() function to get the current time in seconds since the epoch.

To run this model:

$ openmodelica Epoch.mo
Current time: 1679012345.678
Seconds since epoch: 1679012345.678
Milliseconds since epoch: 1679012345678.0
Nanoseconds since epoch: 1.679012345678e+18
Converted time: 1679012345.678

Note that Modelica doesn’t provide built-in functions for millisecond or nanosecond precision, so we’re calculating these values manually. Also, there’s no direct equivalent to converting integer seconds or nanoseconds back to a time object, so we’re just demonstrating getting the current time again.

Next, we’ll look at another time-related task: time formatting and parsing, which may require additional libraries or external functions in Modelica.

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Epoch in Modelica