Why do Bahai's use 19 month calendar?

The regular calendar for Bahai religious events has 19 months of 19 days, giving 361 days, plus 4 or 5 intercalary days which come all together, just before the month of Fasting, like carnival comes before Lent.

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Why? Because the Bab was fascinated with the number 19 perhaps?

Because each religion has its own religious calendar so we had to have our own?

Because this way, we diplomatically slide out from having to agree with either the Jews or Christians or Muslims about whether the day of prayer if Friday, Saturday or Sunday?

or more simply:

Why not?