Determining the appropriate timezone, DST value and UTC offset are all challenging aspects of calculating astrology charts. Yet these are extremely important values to determine correctly in order to calculate an accurate chart.
While this isn’t the place to go into the topic in depth, one simple way of explaining the problem facing every astrologer is this:
How do we know whether Daylight Savings Time was in effect or not?
The only way to ever know for sure is to research local records such as newspapers or governmental policy documents to see if Daylight Savings Time was in effect or not in that location and at that time.
The Internet Assigned Numbers Authority (IANA) provides a free, open-source and widely distributed timezone database (called the IANA TimeZone Database) for managing such concerns.
Fun Fact!
The reason your phone, computer and smart watches automatically adjust when Daylight Savings Time changes is because these devices are using the IANA TimeZone Database.
While the IANA database is accurate and updated regularly, it is less concerned with dates prior to 1970.
This means that charts for years prior to January 1, 1970 require an additional set of timezone and DST rules in order to calculate charts more accurately. Some astrology programs use the ACS Atlas to determine such issues which is an older atlas that doesn’t always receive the most recent updates, especially for newer time periods (post-1970).
LUNA uses a combination of the modern (and standard) IANA TimeZone Database along with a custom and well-researched database of historical Daylight Savings Time changes to account for both the pre and post 1970 time periods as accurately as possible.
What if the chart is different in LUNA® than in other apps & websites?
Unfortunately, there is no standard, open-source version of a pre-1970 timezone database for use in the astrology software world. This means that all of the astrology apps and websites could be using any type of timezone database to calculate their charts.
If you see a discrepancy that you want to adjust, LUNA makes it easy by allowing you to manually change the UTC Offset which will override the calculated value from our timezone database.
How to I adjust my chart for DST?
LUNA makes it easy to adjust your chart regardless of what the automatic timezone and DST detection is:
- When viewing the chart in question, select the “Edit” link to open the chart edit screen.
- At the bottom of that screen is information related to the UTC offset, timezone and DST value.
- Select the pencil icon that’s listed next to the UTC offset and you will see a popup window that lets you change this value.
- Enter the UTC offset you want to use instead of the automatic one and your chart will calculate according to the new value.
When you select the “Edit Offset” link, this popup will appear which will let you manually adjust the UTC offset.
In this example, we’ll change the offset to be 4 (four) hours west of UTC instead of 5 (five) hours. This effectively places this chart into Daylight Savings Time.
This chart will now be calculated 1 (one) hour earlier than it was originally. If you want to revert to the original UTC Offset value, select the “Reset” link and all the timezone data will revert back to what it was originally.
Good to Know
You’re not restricted to adjusting the UTC Offset by only 1 (one) hour. You can fine-tune this value as needed by adjusting the hours, minutes or seconds portion of the UTC Offset. However, we don’t recommend doing this unless you fully know and understand what and why you’re doing so.