@arjit what youre asking is not really a splunk item but rather a math question.
time is a unit of measure. I can't imagine any scenario where what you're asking would be advisable. If you need to show more than one measure of time on the x axis, then my suggestion would be to interpret the question differently.
x would be remain same unit of time
y would display your 4 dimensions measured the same based on the same set of time.
for example if you need to dipslay 4 activities for a specified time, then measure your 4 activities and how well it didi within the specified time.