Historical Time Zone Offsets: Issues
The Historical Time Zone Problem
Astrology software and tables are typically well-made with special attention to the myriad of time changes in the past for the countries, states, and sometimes counties or regions that have used different time zones, daylight saving, war time, and other rules in the past.
Since birth times are highly useful in astrology for constructing charts, we need to know where and when the birth occurred to make any sense of local times.
Of course, when we receive a birth time, it’s a local time that is relative to a particular birthdate, year, and location. This then needs to be converted to a universal time so it’s understood as a particular moment in time.
Essentially, if someone was born at 3:10 AM, we need to know where and when that happened to make any sense of the time.
Let’s say this person was born in Des Moines, Iowa, we still don’t have enough information to convert the time to UT. Yes, Iowa is in the Central Zone which is 6 hours away from UT, but we don’t yet know if the person was born when Daylight Saving Time was observed, which would change that time zone offset to 5 hours.
The year of birth is significant, too, since some time zones changed over the years, and Daylight Saving Time (DST) was not consistently observed. So, for example, if the person was born on June 1, 1975, the time would have been CDT, but if they were born on June 1, 1964, when DST was not observed in the summer, the time would be in CST.
There are some ambiguities in all astrology software programs related to the time zone offsets. While people have put in hard work to research the time zone changes of the past, there remain some unknowns and ambiguities.
Over the years, I have done a lot of work helping people who have written to this site with ambiguous time zones understand the discrepancies, and I thought I would compile some of the notes I have taken from this endeavor below in case it can be of some help to others.
Some discrepancies and/or unknowns:
In the US:
The years from 1919 to the early 1940s:
If you were born between 1920 to 1940, it’s difficult to confirm whether or not DST was observed in many states. There were no concrete regulations and the observance of DST was up to the states to decide. Timeanddate.com has some records that date back to these years for certain cities, for example, Los Angeles and New York.
The years 1961 to 1966 and especially 1965 and 1966 for births in the US:
There are discrepancies in the software atlases and offline tables for these particular years especially. In 1966, the Uniform Tax Act went into effect and helped with regulation of the observance of DST, but this was put in effect only in 1967. Some states were already using DST for years at this point (for example, California) while others had just resumed the observance of DST in 1965 and 1966.
I found a newspaper archive for April 25, 1965, in Idaho which provided a map of the US showing various states that were currently partially using DST, completely observing it, and not observing DST. The list was as follows:
To summarize, in 1965, this paper said that Daylight Saving Time was in effect in 19 states plus D.C., and in part in 11 other states. It mentions that the newcomers to the observance of DST were Colorado, Yatesville, Pennsylvania and no other community in Pennsylvania.
The 19 states the paper said were changing their clocks for DST in April 1965 were California, Colorado, Connecticut, Delaware, Illinois, Iowa, Maine, Massachusetts, Minnesota, Nevada, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont, Washington, West Virginia, and Wisconsin. Add to this District of Columbia.
The paper went on to say that the 11 states only partially observing Daylight Time were Idaho, Indiana, Kentucky, Maryland, Missouri, Montana, New Mexico, Ohio, Oregon, Michigan, and Virginia. The remainder of the states were still on Standard Time.
History.com says that “In 1965 there were 23 different pairs of start and end dates in Iowa alone, and St. Paul, Minnesota, even began daylight saving two weeks before its twin city, Minneapolis. Passengers on a 35-mile bus ride from Steubenville, Ohio, to Moundsville, West Virginia, passed through seven time changes.” This was before some order was brought to the question of DST with the Uniform Time Act in 1966 that was put into effect in 1967. However, in 1966, it follows that some states were using DST in full or in part.
Another example from a newspaper in Pennsylvania (Somerset Daily) on April 29, 1961: “Lewiston, Idaho, for example, is going on Daylight Saving Time while the rest of the state remains on standard. The situation will be similar in the area around Elgin Air Force Base, the only section of Florida going on Daylight Time. Other states where the time standard will vary from area to area are Iowa, Kentucky, Maryland, Missouri, Montana, New Mexico, Ohio, Virginia, and West Virginia.”
Further, some places started DST on a different date (not always the last Sunday in April) and still more ended DST on a different date than others (it usually was the last Sunday of September OR the last Sunday in October). For example, until a law passed in 1955, New York state observed DST until the last Sunday in September, after which it observed DST until the last Sunday in October.
Another example from a Pulaski, Virginia newspaper states that 35 towns and cities and 24 counties in Virginia switched to DST while 74 counties remained on EST in April 1961, and this was due to a patchwork adoption of DST in Virginia.
I have compiled many such notes from old newspapers to help people born in certain states listed just above during these birth years in the summertime. If you’d like help with this and you want to research the time zone offset for your birthdate, I can share some of my relevant notes from scouring old newspapers: Let me know at firstname.lastname@example.org. Keep in mind, though, that it’s quite confusing, even with all of my notes! There are also rich sources of archived newspapers online.
Births from 1967 forward in the US are much more straightforward:
Records are far more extensive and time zone offsets much less ambiguous for births from the year 1967 in the US forward. Even so, there are many different time zone changes, some of which may not be represented accurately in astrology software.
The Chicago Illinois Area Issue of DST/ST before 1960:
Regulation in force in Chicago and area in the 50s stated that hospitals were required to record births that occurred when DST was observed in Standard Time! In other words, if a baby was born when the clocks read 12:00 PM, the birth was to be recorded as occurring at 11 AM. This regulation ended in 1959. We have no way of knowing how many followed this rule. If times were relayed by mouth or recorded in a baby book, the DST value should be used. I first learned of this problem using the Sirius astrology software program that includes a pop-up alert for affected dates and was grateful for this information since it can change a chart by an hour. It’s certainly not the end of the world when this happens, but it’s good to know what you’re dealing with.
Different astrology software programs treat this issue differently. Some use Standard Time during the periods when DST was observed because of this regulation with alerts and options to change to DST, while others use DST during the DST periods by default.
If you were born during this date range in the Chicago area when Daylight Saving Time was in effect, first check to see if your time came from a birth certificate or official registry. If CST is written next to the time, it’s likely but not guaranteed that the time was converted to Standard Time, and you should then assume the time given was in CST. If the time of birth was conveyed by a parent/guardian who observed the time and DST was in effect, then you can probably use CDT.
Our Free Report Section – Notes on Time Zones:
For the above reasons especially, I have always asked users to check their birth data with us at email@example.com to double-check the given time zone offset is correct. This goes double for people born in the regions during the years mentioned above since there was some real chaos in some states before 1967.
The following are some known discrepancies that I have left alone in the database either because they are confirmed accurate or until further research suggests otherwise. While there is a note marked “Important” on our birth chart calculator page to double-check birth dates/times with us and we check many dates every day, the assumption is that some will ignore or overlook this message, and others will do their own research.
In addition to the general notes above, some of my notes on the software are as follows (these are known time zone discrepancies between astrology software and the chart service on this site, and reasons why I am keeping them):
- For Indiana in the Gary area which affects several cities and towns, we have 1963 to 1967 recorded with no time changes which is also shown to be the case on timeanddate.com. However, to date, this is not recorded in most astrology software. I am leaving this discrepancy in because it looks to be accurate.
- For Michigan, most astrology software treats all of 1968 as observing Standard Time, but DST was in force according to timeanddate.com as well as my research into old newspapers (the newspapers completely confirm that DST was in observance in 1967 and 1968, after which it was not observed for a few years, until 1973). So, the software on this site recognizes DST in 1968 in Michigan since I’ve confirmed it’s accurate.
- We have DST observed in 1990 as an anomaly in the Philippines while some astrology software doesn’t recognize this. Because it is confirmed accurate, I have kept it.
- All of the Northern Idaho cities are shown as observing DST from 1961 forward, but not in 1965, in the major software programs. I have found conflicting information in old newspapers. For example, I have seen references to Lewiston only observing DST during this period while the remainder of the state didn’t. Also, I don’t know what the reason was for the 1965 standard time anomaly for all Northern Idaho cities, not just Lewiston. Because I can’t substantiate the reason for these, I am leaving the software’s database in the Free Report section be (it records DST as starting in 1965 in Northern Idaho cities).
- We have always assumed CDT for the ambiguous Chicago area DST/ST births noted directly above, but I am adding a “Time Zone Not Sure” message for these birthdate ranges so that people have the option to change the time zone if they feel their birth time was converted to CST.
- Two and a half counties in South Dakota (Todd, Mellette, and east Stanley) are in the Central time zone according to many different sources but are treated as in the Mountain zone in many astrology software programs. We have these as in the Central time zone and I am keeping the associated cities in the Central zone since evidence points to this being correct.
- The Xinjiang and Tibet provinces of China are officially using Beijing time, but unofficially observe Xianjing time in certain areas –a 2 hours’ difference. I am using the schedule as relayed in timeanddate.com that changes the zone from Xianjing time to Beijing time on May 1st, 1980. Some software programs make this changeover in 1960 and others in 1970. Especially with such a large difference, it’s best to investigate whether your birth time was recorded in Xinjiang time or Beijing time.
As people write in checking their birth data for the free report section, the time zone database is getting sharper. However, it’s always important to know that in all programs, some time zones may be inaccurate because they are unknown. The current source that seems to be the best for historical time zones as they relate to astrology is astro.com since it combines various sources, so checking your data with them makes sense for dates/areas that have DST issues before 1967.
See Also: Using the Free Report Section.