Dear colleagues,
I've tried and tried and tried, but to no avail. I'm attempting to substantiate that the correct symbol for year is simply 'y', and not (for instance) 'yr'.
Can anyone here give me a reference to that effect? Preferrably from BIPM itself. I surfed there today for like an hour without ANY success.
And, yes, I'm *desperate* because I need to provide this reference by the end of today!...
:-S Sorry about the urgency...
Any help is very appreciated.
Marcus
There is no official BIPM symbol for the year, probably because it is hard to define just what year is meant.
There is the sidereal year which is the time required for the sun to move from any position with respect to the stars, as seen from the earth, to the same position again. Its length is 365.25636 days.
The anomalistic year is the interval of tome required for the earth to revolve from the perihelion point of its orbit around to the perihelion point again. Its length is 365.25964 days.
The tropical year is the interval of time required for the sun to move (apparently) from an equinox around to the same equinox again. This is the year that is usually meant. The tropical year is shorter than the sidereal year by the time required for the sun to move eastward by 50" in its annual apparent motion among the stars. In mean solar time, the length of the tropical year is now 365.24220 days. The tropical year is decreasing in length at the rate of about half a second in 100 years, but its length will increase again.
The CIPM decided in 1956 that "the second is the fraction 1/31 556 925.9747 of the tropical year for January 0 at 12 hours ephemeris time." This decision was ratified by the 11th Conf�rence G�n�rale des Poids et Mesures (CCPM) of 1960.
