palani
23rd September 2012, 10:34 AM
Here is a website where you can enter your latitude and longitude and determine the equation of time for your location.
http://www.spot-on-sundials.co.uk/calculator.html
Why would you want to?
Well, it seems like the push for Universal Time made life much easier for any service providing transportation schedules but it also is the function of the sovereign to determine the time he/she is going to use. In Iowa Title 1 of the Iowa code is labeled "Sovereignty" as follows
1D.1 Standard time and daylight saving time.
The standard time in this state is the solar time of the ninetieth meridian of longitude west of Greenwich,* commonly known as central standard time, except that from two o'clock ante meridiem of the first Sunday of April in every year until two o'clock ante meridiem of the last Sunday of October in the same year, standard time shall be advanced one hour. The period of time so advanced shall be known as "daylight saving time."
1D.2 Effect of time change.
In all laws, statutes, orders, decrees, rules, and regulations relating to the time of performance of any act by any officer or department of this state, including the legislative, executive, and judicial branches of the state government, or any county, city or district thereof, relating to the time in which any rights shall accrue or determine, or within which any act shall or shall not be performed by any person subject to the jurisdiction of this state and in all the public schools and institutions of this state, or of any county, city or district thereof, and in all contracts and choses in action made or to be performed in this state, the time shall be the time established in section 1D.1.
Now I don't object to the State deciding what time they are going to use as standard but their decision has little to do with how I view time. The effect of the equation of time is to determine when local noon appears at my precise latitude and longitude for any given day of the year. Now this may be determined quite easily if one has a pocket sundial with a compass and not too much magnetic variation for the area. If one was in the Iron Range country of Minnesota the magnetic compass is virtually worthless so the pocket sundial would not give an accurate determination of local noon.
With the calculator enter your lat and long for your area and the time zone. You will need to enter w (west) for the longitude and n (north) for the latitude for the north american continent. The result is the difference between your local noon and the "official" time prescribed for you by your State. Every time zone encompasses 15 degrees of longitude and represents one hour of time difference between the previous time zone. The time zones are established as Greenwich, 15 deg w (-1 hour from GMT), 30 deg w (-2 hour from GMT), etc. If you are located west of the meridian established for your time zone then mostly the equation of time is going to place your local noon AFTER the time the sun appears overhead at that meridian.
Julian dates are of use as well but these dates change at noon. In earlier history (several thousand years ago) the start of the day was at SUNSET rather than NOON. I would suggest a modified Julian date be used to get back to the pre-history method. Consult an almanac or online calculator to determine WHEN local sunset is going to occur and then subtract that time from the Julian date.
The goal? When someone says you did something at a particular time and date you might want to have an alternative to counter the "official" version.
http://www.spot-on-sundials.co.uk/calculator.html
Why would you want to?
Well, it seems like the push for Universal Time made life much easier for any service providing transportation schedules but it also is the function of the sovereign to determine the time he/she is going to use. In Iowa Title 1 of the Iowa code is labeled "Sovereignty" as follows
1D.1 Standard time and daylight saving time.
The standard time in this state is the solar time of the ninetieth meridian of longitude west of Greenwich,* commonly known as central standard time, except that from two o'clock ante meridiem of the first Sunday of April in every year until two o'clock ante meridiem of the last Sunday of October in the same year, standard time shall be advanced one hour. The period of time so advanced shall be known as "daylight saving time."
1D.2 Effect of time change.
In all laws, statutes, orders, decrees, rules, and regulations relating to the time of performance of any act by any officer or department of this state, including the legislative, executive, and judicial branches of the state government, or any county, city or district thereof, relating to the time in which any rights shall accrue or determine, or within which any act shall or shall not be performed by any person subject to the jurisdiction of this state and in all the public schools and institutions of this state, or of any county, city or district thereof, and in all contracts and choses in action made or to be performed in this state, the time shall be the time established in section 1D.1.
Now I don't object to the State deciding what time they are going to use as standard but their decision has little to do with how I view time. The effect of the equation of time is to determine when local noon appears at my precise latitude and longitude for any given day of the year. Now this may be determined quite easily if one has a pocket sundial with a compass and not too much magnetic variation for the area. If one was in the Iron Range country of Minnesota the magnetic compass is virtually worthless so the pocket sundial would not give an accurate determination of local noon.
With the calculator enter your lat and long for your area and the time zone. You will need to enter w (west) for the longitude and n (north) for the latitude for the north american continent. The result is the difference between your local noon and the "official" time prescribed for you by your State. Every time zone encompasses 15 degrees of longitude and represents one hour of time difference between the previous time zone. The time zones are established as Greenwich, 15 deg w (-1 hour from GMT), 30 deg w (-2 hour from GMT), etc. If you are located west of the meridian established for your time zone then mostly the equation of time is going to place your local noon AFTER the time the sun appears overhead at that meridian.
Julian dates are of use as well but these dates change at noon. In earlier history (several thousand years ago) the start of the day was at SUNSET rather than NOON. I would suggest a modified Julian date be used to get back to the pre-history method. Consult an almanac or online calculator to determine WHEN local sunset is going to occur and then subtract that time from the Julian date.
The goal? When someone says you did something at a particular time and date you might want to have an alternative to counter the "official" version.