year 0 and ISO 8601 and slider

[gregallensworth]

Refer to OpenHistoricalMap/issues#624

I have made the changes on a branch, but would like them tested before I merge into main, since OHM loads directly from the main branch on Github.

Testing is as follows:

• check out the code git clone https://github.com/OpenHistoricalMap/leaflet-ohm-timeslider-v2.git
• switch to the new ISO-8601 branch: git checkout bce-iso8601-compliance
• start a Python web server: python -m SimpleHTTPServer 9646 or python3 -m http.server 9646
• point browser at http://localhost:9646/ and try it out

[1ec5]

−0.5 is a valid value (around July of 1 BCE). I can get to that date by entering -0000-07-01 into the Change Date dialog but not by dragging the slider.

Bringing up the Change Date dialog again formats the date as “7/1/0”, which is not a valid formatted date. It should say either “-0000-07-01” (raw ISO date) or “7/1/-1” (formatted MDY date). This is a single year being represented as three different numbers simultaneously: “-1”, “0”, and “1 (BCE)”.

If we can’t reuse the dropdown menus in the Change Date dialog, I suggest changing it to not format the date and only accept a raw ISO date for consistency with the range control’s year fields.

[gregallensworth]

−0.5 is a valid value (around July of 1 BCE)

It is valid, but is the same output as +0.5 and both appear in a numeric slider (range input). If I do not have that workaround, then the slider effectively has two copies of 1 BE, the -1 to 0 range and the 0 to 1 range.

I can get to that date by entering -0000-07-01 into the Change Date dialog but not by dragging the slider.

It is working for me. See screengrab below. Can you describe the problem in more detail?

[1ec5]

It is valid, but is the same output as +0.5 If I do not have that workaround, then the slider effectively has two copies of 1 BE, the -1 to 0 range and the 0 to 1 range.

I made a typo above yet again. To clarify, this is what I would expect:

ISO 8601	Filter decdate	en-US format	Explanation
-0001-01-01	−1.0	1/1/2 BCE	Beginning of the year 2 BCE
-0001-07-01	−0.5	7/1/2 BCE	Middle of the year 2 BCE
-0000-01-01 0000-01-01	0.0	1/1/1 BCE	Beginning of the year 1 BCE
0000-07-01	0.5	7/1/1 BCE	Middle of the year 1 BCE
0001-01-01	1.0	1/1/1	Beginning of the year 1 CE

It is working for me. See screengrab below. Can you describe the problem in more detail?

jump.mov

[gregallensworth]

I'm going to close this PR and the bce-iso8601-compliance branch, and revisit from a different angle, fixing the decimaldate math. I think Minh is right that the best order of operations is:

• localization stuff in Improve date readouts to use locale instead of fixed mdy/dmy behavior issues#626 which can result in a few simplifications and dependencies
• fix decimaldate.decimal2iso() so that -0.5 and +0.5 are not the same (-1 from year if <0)
• then UI improvements to prevent confusion as to why 0 becomes -1, =1 becomes -2, etc.