What does RDA means? Please help!

[PanzerElite]

Hello Collectors,

What does RDA means? it appears in the promotion documents,
and with a date following (but the following date is superior to the date of the document itself), i think it means "the former date of promotion"?
am i right? but RDA for what words?

thank you!
Jason

[Simon O.]

Good explanation of a very complex system
http://www.camp198.fsnet.co.uk/Rangsdienstalter.htm

[PanzerElite]

Thank you Sir with your prefessional researching.
it seems i have to spend much time to read and understand it,
very complex it looks.