Why is the Memorial Being Observed On Purim instead of the Passover, Nisan 14?

Yes but you have to be careful. As the Watchman explained there are years where an extra month is inserted into the calendar year. Check his comment earlier in the thread.
We also have to remember that according to Jehovah's calendar, the Jewish day begins from Evening to Evening.

The term “Passover” is appropriately used to describe the events of either the 14th day of Nisan on which the lamb was originally slain, or the 15th day of Nisan on which the feast was begun. Today, a lamb is no longer slaughtered by the Jews so that less emphasis is placed upon the 14th and the current Jewish calendar does not give it any significance. It is the 15th day which is now exclusively emphasized, commemorating the feast and the exodus from the land of Egypt. This explains why the Jewish calendar marks only the fifteenth day of Nisan as the “Passover” (the major portion of the day, but not its actual beginning). The previous day is the 14th of Nisan, and it is this day that concerns us.

Further, because the Jewish day commences at six o’clock in the evening, Nisan 14 actually begins on the day marked Nisan 13 on the Jewish calendar. After six p.m. on the day shown as Nisan 13 is the appropriate time for our Memorial celebration. Thus, the Memorial falls a day prior to the published Jewish calendar date for Passover (Nisan 15).

I will be observing the Memorial on Sunday, April 21st​
 
We also have to remember that according to Jehovah's calendar, the Jewish day begins from Evening to Evening.

The term “Passover” is appropriately used to describe the events of either the 14th day of Nisan on which the lamb was originally slain, or the 15th day of Nisan on which the feast was begun. Today, a lamb is no longer slaughtered by the Jews so that less emphasis is placed upon the 14th and the current Jewish calendar does not give it any significance. It is the 15th day which is now exclusively emphasized, commemorating the feast and the exodus from the land of Egypt. This explains why the Jewish calendar marks only the fifteenth day of Nisan as the “Passover” (the major portion of the day, but not its actual beginning). The previous day is the 14th of Nisan, and it is this day that concerns us.

Further, because the Jewish day commences at six o’clock in the evening, Nisan 14 actually begins on the day marked Nisan 13 on the Jewish calendar. After six p.m. on the day shown as Nisan 13 is the appropriate time for our Memorial celebration. Thus, the Memorial falls a day prior to the published Jewish calendar date for Passover (Nisan 15).

I will be observing the Memorial on Sunday, April 21st​
I think as long as we remember the sacrifice Jehovah and Jesus made for us they will be happy we did so. They are readers of hearts, and if one believes one day over another is correct in light of the confusion a leap year creates in the modern Jewish calendar, i'm sure they will understand. If we go by the old Jewish Calendar however, March 24th is the correct date because it is the first full moon after the spring equinox.
 
Sí, pero hay que tener cuidado. Como explicó Watchman, hay años en los que se inserta un mes adicional en el año calendario. Consulte su comentario anteriormente en el hilo.

Yes but you have to be careful. As the Watchman explained there are years where an extra month is inserted into the calendar year. Check his comment earlier in the thread.
God said in his word in the Bible that we would have to add an extra month in certain years, or rather has he given us the lights to know when the sacred celebrations fall?... If we had to add an extra month, don't you think that should our God have informed that?... 🤔
 
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