A location can have different coordinates... even though it is stationary ...
the reason? the datums are different
this applies to any method of denoting location... geographic coordinates (aka longitude/latitude) or projected coordinates (eg UTM, Albers, State Plane in either feet or meters)
The datum is the "model" used to describe earth... no datum? datum not known? coordinates could be off by a little or a lot, depending on the datum.
So, the coordinate system needs to be know (projected or geographic)
The units need to be known (meters, feet, decimal degrees, etc)
AND the datum
Missing one of the above? Get it
... sort of retired...