[c54]

To a local observer yes, but to someone moving at a different speed no! FloatHeadPhysics does a good job explaining some of this https://youtu.be/OpOER8Eec2A

[layer8]

No, time still passes at one second per second for any observer.

[lxgr]

Only if you disregard observers in different frames of reference interacting with each other, which you shouldn't when you need high precision and it comes to projects spanning Earth, Earth orbit, and the Moon.

GPS wouldn't work without accounting for relativity, for example.