We have been saying since 2005 in our paper at physicsnext.org that, while different observes will measure different times in many cases, Einstein time-dilation equations are wrong, and we give the correct equations.

FORBES: New Evidence Casts Doubt On Faster-Than-Light Neutrinos

Working on a theory to combine quantum mechanics with Einstein's special relativity, he realised his equations predicted a corresponding anti-particle for every particle in existence - identical in every respect, but with an opposite electrical charge.

BBC: The problem with anti-matter

Thus, Einstein introduced his cosmological constant as an ad hoc factor in his equations, in order to conform with observational cosmology of the era which called for a static universe.

FORBES: Dark Energy Camera Could Reshape Einstein Cosmology