If interested to “drill” further, there must be many alternatives to search for. Online plug-in calculators and the like. The sites themselves may come and go, depending on the funding behind it.
It makes sense to me - time dilation is a proven real thing. Fascinating to the imagination, obviously this ‘aint happening anytime soon. You can travel at .95c, but getting there will be a hurdle!
I’m interested in the exact relationship between relativistic speeds and time dilation. I’ve had a story in my head for years in which that relation is a major plot element, but I’ll never write it unless I can quantitate that relationship. And I’m a biochemist, so I learned to quantitate, never quantify...