You can do the unit conversions yourself. They aren't that difficult to do. From the documentation for currentUnit -time:
Set the current time unit. Valid strings are:
[hour | min | sec | millisec | game | film | pal | ntsc | show | palf | ntscf]
When queried, returns a string which is the current time unit
Note that there is no long form for any of the time units. The non-seconds based time units are interpreted as the following frames per second:
game: 15 fps
film: 24 fps
pal: 25 fps
ntsc: 30 fps
show: 48 fps
palf: 50 fps
ntscf: 60 fps
So lets take palf as a current unit of time and you want to convert it to milliseconds.
That means that 50 frames = 1 second. Or, 50 frames = 1000 milliseconds. Which is equivalent to saying 1 frame = 20 milliseconds.
So what you can do is query the current unit of time via:
currentUnit -q -time;
Based on the string result you can convert it to milliseconds as shown above.
So for the palf conversion it would look like:
proc float currentTimeInMillisecs()
{
float result = 0.0;
float $time = currentTime -q;
string $unit = currentUnit -q -time;
if( $unit == "palf" )
{
// 50fps is equivalent to saying 1 frame = 20ms
//
$result = $time * 20;
}
// ... Process other unit types
}