vx.ClockA singleton object that handles timing.
As this is an internal object, you cannot create your own Clock object. This simply represents the type of a variable in the vx library. Just use the variable vx.clock to use this.
vx.Clock.timer -> number (read/write)
vx.Clock.systemtime -> number (read)
timer variable can be written to unlike systemtime, which may be useful for timing some operations. Although, really, you can get away with just using timestamps and not ever modifying the timer. Ah well, the option's there.