On Wed, 12 Jun 2024 11:34:15 -0500, Mike Schwab wrote: >If I remember correctly, the timestamp runs from 1900 to 2042, >checking 1 high bit gives you 2 X 71 year epochs, 2 high bits gives 4 >X 35.5 year epochs, 3 high bits gives 8 X 15.75 year epochs, 4 high >bits 16 X 7.875 year epochs. > >Suggest checking 2 high bits, treating current and past 2 epochs (71- >106.5 years) as valid, and the next epoch as past data that needs to >be cleared before reuse. From now to 2042, the future epoch of >b'00'did represent 1900-1935 so no past data, but starting in 2042 the >next epoch of B'01' currently used to represent 1936-1971 and might >have some data to be flagged. > Why so complicated? I had imagined the Epoch Index as simply an 8-bit leftward extension of the TOD, extending the range from 142.713391 to approximately 36,534 years.
What's the significance of 35 years, other than that it's 1/4 of 142? I was dismayed that the ETOD was not defined as signed. I feel that dates in the 19th Century and even back to the 1st are more relevant than the 380th. Format conversion through that range is hardly meaningful. It would be overwhelmed by ΔT, hours in historic times: <https://en.wikipedia.org/wiki/%CE%94T_(timekeeping)>. -- gil ---------------------------------------------------------------------- For IBM-MAIN subscribe / signoff / archive access instructions, send email to [email protected] with the message: INFO IBM-MAIN
