Einstein told us that the speed of light must always, not only appear, but BE the same in every frame of reference no matter how fast we are moving towards or away from it. So even if you are moving at half the speed of light towards a light beam, the entire universe must conspire to either "speed up" or slow down your "time" to account for this difference.
If that makes sense to you, you are no longer sane. You cannot create scenarios of two mutually exclusive events at the same time and call that reality. This is fundamental to reason.
To show this contradiction, consider you are running away from a light beam and towards another at the same time. You move at half the speed of light. Of course in real life you will encounter the light you are moving towards first, but in Einstein's universe both beams MUST (in your world) hit you at the same time. However, in Einstein's universe, someone else will see them hit you at different times because they also MUST see light travel at a certain speed. This is just plain fucking stupid.
At best you can have an illusory effect, but to confuse that with a real difference in simultaneity is to truly give up on reason itself.
The source of one of the beams of light and away from the source of the other. Assume both sources are at a fixed distance from each other.
The light you are going toward (constant speed) will appear blue shifted.
The light you are going away from (constant speed) will appear red shifted.
You would see blue in front, red in back.
The time dilation occurs when you are under acceleration. To slow down time, you would have to accelerate away then accelerate back.
It may be blue shifted but it will hit you first. Anything else creates two mutually exclusive realities which defies basic logic.
Einstein's equations have no parameter for acceleration. So those who make this claim need to invoke a different theory. SR is based on inertial "frames" moving at constant velocities. No acceleration is invoked to derive the equations for "time dilation".