This statement is false if we speak about the time. The time zones decrease as we go westward from the Greenwich Meridian. Look at the time zones map found on dayspedia.com:
However, since the Greenwich Meridian is the Prime meridian, that is, it has zero longitude, values to the west of it decrease and are sometimes considered positive or have west attached to them like "Reykjavík, Iceland is located 21° 49' 39.9864'' West, which means that its longitude is -21.827774". Therefore, if we speak about the longitudes, this statement is half false and half true.
Source of the image:
I think it is false because values on west of longitude are negative