Thanks for writing. Hebcal agrees with the conservative Luach, which is published by Rabbi Miles Cohen. See below:

We will investigate further why some books list this as 31:1-19 and others list as 31:2-20.

For example, Mechon Mamre lists chapter 31:1 as Ko amar Adonai matza chein bamidbar

https://mechon-mamre.org/p/pt/pt1131.htm

The Hebrew date converter is not designed to be accurate for year 1752 C.E. and earlier.

Hebcal does not take into account a correction of ten days that was introduced by Pope Gregory XIII known as the Gregorian Reformation.

Where do you see י״ד טבת תתק״ס on Hebcal.com for 1/1/2200 ? Here is what we see:

https://www.hebcal.com/converter?gd=1&gm=1&gy=2200&g2h=1

• Wed, 1 January 2200 = 13th of Tevet, 5960
• י״ג בְּטֵבֵת תתק״ס

After you've created your personal yahrzeit + anniversary calendar, you can subscribe to email reminders after saving your calendar.

First, click the grey Save button near the top of the page

Then, fill out your email address and click the blue Save button

A confirmation message will be sent to your email address. Click the link within that message to confirm your subscription.

Thanks for using the Hebcal Yahrzeit + Anniversary calendar. Since the focus of the website is on Hebrew calendar and most regular calendar apps (Apple, Google, Outlook, etc) can already handle repeating/recurring Gregorian events, this hasn't been a very high priority for us. We will take this idea under consideration.

Glad this worked for you. Shabbat shalom & shana tova!

Several websites (Hebcal, Chabad, TorahCalc) all agree that Sun, September 29, 2239 = 29th of Elul, 5999.

Perhaps there's an error in your VBA program?

Hi, we've made a temporary workaround where Google Calendar reminders will be fixed to either Israel Time if you check the "Israel Yizkor schedule", or Eastern Standard Time for all other calendars. This is not a very ideal fix, as it delivers Yahrzeit candle reminders at the wrong time for other locations, but it will work for a large fraction of the Hebcal user base.

Thanks for using Hebcal. Your device is using light/dark appearance switching automatically.

Depending on what kind of device you use, you can follow instructions like the following to enable or disable the automatic change from light mode to dark mode

Windows

https://support.microsoft.com/en-us/windows/change-colors-in-windows-d26ef4d6-819a-581c-1581-493cfcc005fe

macOS

https://support.apple.com/guide/mac-help/use-a-light-or-dark-appearance-mchl52e1c2d2/mac

Android:

https://support.google.com/android/answer/9730472?hl=en

iPhone and iPad

https://support.apple.com/en-us/108350

Hi, thanks for using Hebcal and the Google Calendar integration. We're sorry to hear that you're having difficulty seeing an integrated view and are now seeing a separate parallel day. Unfortunately, we can't help much here - we haven't made any change on our end that could cause your Google calendar daily view to appear any differently. 

Perhaps there is a setting you can change on the Google Calendar side?