This is updated for last post.
Originally, in the 18th century, the meter was described as the length of a pendulum with the half-period of 1 second! Which does base distance on time, but unfortunately also gravity. Which slightly varies across earth causing this to be inaccurate. This is when the French Academy of Sciences came in and took over the definition of a meter (damn metre). They described it as one ten-millionth of the length of the equator to the north pole. They used a longitute which passed through Paris.
There were many intermediary definitions of a meter between then and now (1983), see Wikipedia - Metre. Long story short, the General Conference on Weights and Measures defines the meter (as of 1983) as “the distance travelled by light in a vacuum during a time interval of 1⁄299,792,458 of a second.”
The subsequent definitions of the meter after the French took it over was essentially aimed at refining the precision of the definition no matter where you may need to be calibrating. I’m not clear on this, but it seems they made one refinement due to a miscalculation because of the assumption that the earth was flat. This made the meter 1⁄5th of a milimeter longer.
Tags: time, meter, metre, distance, length, measurement, travel, second, gravity, metric
