According to Halachic Rulings of the Alter Rebbe's Shulchan Aruch and Chabad Custom.Prepared under the guidance of Rabbi Sholom Ber Chaikin
The calendar is laid out according to the Hebrew months, with the civil calendar date noted on each day. There are improvements in the graphics, changes in the format of the symbols used, and clarifications of and additions to the text digest.Why is it important to use a Hebrew calendar?
(Jewish law) mandates the use of a Hebrew calendar to calculate the times required to abstain from marital relations in anticipation of a period. The Hebrew date begins at shkiah
(sunset) and ends the following day at shkiah
(whereas the civil date, based on the standard solar calendar, begins and ends at midnight). All menstrual calculations are only according to the Hebrew calendar.
Calculations based on any other calendar are inaccurate. Never use the standard solar calendar for this purpose
although, for reference only, this personal calendar includes civil dates.
This calendar conveniently uses the same layout and symbols as our online calendar
and is meant to work in tandem with it. Please note that our online calendar does not replace the halachic requirement of keeping your own written calendar which can be fulfilled through using this calendar.