Why was the finale pushed back to May, 1988?

[MagnumFan]

I was reading when the various seasons/episodes aired. The second to last episode aired in February 1988. Why was the finale delayed until May?

[rtc]

The series finale IIRC was "saved" for May 1st '88 to run during "Sweeps Week",the
last ratings period of the '87-'88 season.

It did very well,too.

I came late to MPI,missed it on its original network run back then.
Have since caught up and have had every question answered
but one:

When was the very last scene filmed?

The former set decorator said on his site that it took 45 days
from first scene of a show to air date...a month and a half.
If you look at the seasons and do the math it works out to
maybe 3 or 3 1/2 shows a month being produced.

But the final season defies this.The 2001 E! Entertainment
show said that "filming concluded in late '87" but a picture
in the "behind the scenes" section here on this site shows a
clapboard with 3-4-88 on it plain as day.

Larry Manetti also confirmed this in an email late last year.

So what happened?
Was the final scene somehow ruined in processing and they had to
redo it?
Did they up and take a month off for some reason?
Guess we'll never know.
(Not even The Shadow knows.)