Re: [LEAPSECS] JD & MJD, UT1 & UTC

2017-01-02 Thread Zefram
Tom Van Baak wrote: >But since some of you are real picky about formal definitions, >my question is what to do about MJD -- is it UT1-based or it is >UTC-based? Both. Also TAI, TT, TCG, and TCB. And UT0, UT2, UT1R, UT2R, UTC-SLS, and other flavours of UT. The use of JD or MJD doesn't imply

Re: [LEAPSECS] JD & MJD, UT1 & UTC

2017-01-02 Thread Steve Allen
On Mon 2017-01-02T12:55:23 -0800, Tom Van Baak hath writ: > But since some of you are real picky about formal definitions, my > question is what to do about MJD -- is it UT1-based or it is > UTC-based? And if UTC-based, what's the right thing to do when the > day has a +/- leap second? IAU

[LEAPSECS] JD & MJD, UT1 & UTC

2017-01-02 Thread Tom Van Baak
Now is a good a time as any to bring up an issue I've been meaning to ask. My understanding is that JD has always been a day count, based on rotations of the earth. So the timescale from which JD is calculated is UT1 (not TAI or UTC). JD is widely used in astronomy. Presumably when JD is

Re: [LEAPSECS] Time math libraries, UTC to TAI

2017-01-02 Thread Richard Langley
And more here: http://www.hermetic.ch/cal_stud/jdn.htm -- Richard Langley - | Richard B. LangleyE-mail: l...@unb.ca | | Geodetic Research Laboratory Web:

Re: [LEAPSECS] Time math libraries, UTC to TAI

2017-01-02 Thread Pierpaolo Bernardi
On Mon, Jan 2, 2017 at 9:10 PM, Clive D.W. Feather wrote: > Michael.Deckers. via LEAPSECS said: >> It is the Julian day numbers used in astronomy that >> take integral values at noon epochs -- but they have nothing to do with >> the Julian calendar, except perhaps

Re: [LEAPSECS] Time math libraries, UTC to TAI

2017-01-02 Thread Clive D.W. Feather
Michael.Deckers. via LEAPSECS said: > It is the Julian day numbers used in astronomy that > take integral values at noon epochs -- but they have nothing to do with > the Julian calendar, except perhaps for the origin of the name. Not even that - I thought Julian days were named after

Re: [LEAPSECS] Time math libraries, UTC to TAI

2017-01-02 Thread Michael.Deckers. via LEAPSECS
On 2017-01-02 18:55, Brooks Harris wrote about the correspondence | Date| MJD| NTP | NTP Timestamp | Epoch| | 4 Oct 1582 | -100,851 | -3 | 2,873,647,488 | Last day Julian | Ah, I think the table is correct - that's the infamous reset made by

Re: [LEAPSECS] Leap seconds still broken

2017-01-02 Thread Tony Finch
Some vague reports of leap-second-related CDMA network outages (note, not load related since the leap second was several hours before new year in the USA) https://news.ycombinator.com/item?id=13294747 Tony. -- f.anthony.n.finch http://dotat.at/ - I xn-- zr8h punycode