Standard unit symbols

[eevleevs]

The following units use non standard symbols. Please consider updating: tonm -> t hr -> h day -> d

The following have alternatives which should be included: yr -> a L -> l

References:

• https://en.wikipedia.org/wiki/Non-SI_units_mentioned_in_the_SI#Units_officially_accepted_for_use_with_the_SI
• https://en.wikipedia.org/wiki/ISO_80000-3