The Chart Library Doctor helps you check the birth times of charts you imported from MMI desktop. For most imported charts, MMI desktop and Maia Mechanics agree on the birth time. For some, they don't, usually because of how the clock at the birth place worked at the time. The Doctor lists those charts, shows you both times side by side, tells you whether the difference changes the chart, and lets you choose which time each chart should use.
Nothing changes until you choose. Any chart you leave unchosen stays exactly as it is.
To open it, click on Tools and select the Chart Library Doctor.
Why two times?
A birth time is recorded on a local clock. To calculate a chart, that local time has to be turned into Universal Time (UT), and that depends on the clock rules at the birth place on that date: its time zone, daylight saving, or before standard time, the town's own clock (local mean time).
MMI desktop is the birth time stored in your MMI file, the one the desktop app showed.
MMI Online is the time Maia Mechanics works out for the birth place. From 1970 it uses the TZ Database. Before 1970 it uses the ACS Atlas where the atlas knows the town's own clock (local mean time, and US and Canadian towns), and the TZ Database everywhere else.
When the two sources put the birth at different moments, the chart appears in the Doctor.
The tabs
Charts are grouped into tabs. The tabs where you choose between two sources come first, because those are the decisions that matter most.
Choose a source
Local mean time: births recorded on the town's own clock, before standard time. MMI desktop and MMI Online place that clock slightly differently.
Before 1970: MMI desktop and MMI Online use different time zone rules for these towns, often daylight saving.
From 1970: MMI desktop's time zone for the town differs from the TZ Database, which MMI Online uses for every birth from 1970.
Restore your file's time?
Moved by an import: an earlier import changed these charts' times. You can restore the time in your file, or keep the current one.
File times disagree: the local time and UT in your file don't match. MMI desktop used the UT.
Place not found: MMI Online could not place these towns, so it has no time of its own.
Entered in UT: your file has these births entered in UT, and an earlier import read them as local times.
Each tab shows how many charts it holds, and how many you have chosen so far (for example 3/44).
Reading a row
Each row shows the chart's name, birth place and local birth time, then the two times it could use. A Current marker shows which time the chart uses now.
Difference: how far apart the two times are, from a few seconds to several hours.
Effect on chart: which properties or activations change between the two times, for example Profile, Sense or Moon line. This tells you at a glance which choices matter.
Recommended: shown next to MMI Online where both the ACS Atlas and the TZ Database agree with MMI Online's time and MMI desktop matches neither.
Rows where the two times give the same chart are gathered at the bottom of each tab under Same chart either way. The times differ, but no property or activation changes, so the choice doesn't affect your reading. Click Show to see them.
Compare in the Birth Window
Click Compare on any row to open both times in the Birth Window. Both times are marked on the timeline, and each row shows whether its value changes between them. This is the best way to check every change, down to each planetary activation.
Both times are read on the chart's current clock. For example, a birth in Enid, Oklahoma, on July 1, 1955, entered at 10:00, reads ACS Atlas 10:00 · TZ Database 09:00. The hour between them is the disagreement.
You can hover over any block to see its value. Charts can't be opened from the timeline in this view, because the Doctor's charts don't yet have a settled time zone to calculate from.
Compare needs the Essentials plan or higher.
Making your choices
Use the switch at the end of each row to choose a time. In the Choose a source tabs the options are MMI desktop and MMI Online. In the Restore your file's time? tabs they are Keep current and Restore file.
To choose for many charts at once:
Use all recommended at the top chooses MMI Online for every recommended chart in every tab.
The buttons beside each tab's title apply one choice to every chart in that tab.
The bar at the bottom counts your choices. When you're ready, click Apply choices.
Which time should I choose?
If a chart is marked Recommended, MMI Online is the safer choice.
Keep MMI desktop when you know the birth was recorded on a different clock, for example an official record that used a time zone the town didn't follow.
If a row says This town name is in more than one time zone: check the place, make sure the birth place is the right town before you choose. Keep MMI desktop if its zone is the birth town's.
If the effect on the chart is Same chart either way, either choice gives you the same reading.
After you apply
The chart's Birth Data tab shows which source its birth time comes from in the Time Zone Database row: ACS Atlas or TZ Database.
Frequently asked questions
Why do some times differ by only a few seconds?
Local mean time is based on the town's exact longitude, so it often includes seconds. MMI desktop rounded some of these times. A difference of seconds rarely changes a chart, which is why those rows usually sit under Same chart either way.
Does the Doctor change charts I created in Maia Mechanics?
No. The Doctor only lists charts imported from MMI desktop. Charts created in Maia Mechanics already use MMI Online's time.