A search for "التوقيت الصيفي" on Ramallah News supports the 2019-03-30 00:00 theory: https://ramallah.news/post/82650/ appears to be dated 18 March 2019, and says (Google's translation):

"Daylight saving time is expected to start in the Gaza Strip and the West Bank on Friday, March 29, bringing the clock forward. Daylight saving time starts on Saturday, March 30, with the clock advancing 60 minutes ahead of midnight on Saturday."

--
Tim Parenti

On Tue, 26 Mar 2019 at 16:55, Paul Eggert <eggert@cs.ucla.edu> wrote:

On 3/26/19 5:26 AM, Sharef Mustafa wrote:

> The Palestinian cabinet announced today that the switch to DST will be
> on Fri Mar 29th 2019 by advancing the clock by 60 minutes
>
> the decree signing date is Mar 12th but it was not published till today.
>
> The decree does not specify the exact time of switch
>
>
> http://palestinecabinet.gov.ps/Website/AR/NDecrees/ViewFile.ashx?ID=e54e9ea1-50ee-4137-84df-0d6c78da259b
>

Ouch. That URL specifies 2019-03-29 (Friday) and uses the same wording
as the following URLs from previous years:


http://www.palestinecabinet.gov.ps/Website/AR/NDecrees/ViewFile.ashx?ID=e7a42ab7-ee23-435a-b9c8-a4f7e81f3817
http://www.palestinecabinet.gov.ps/WebSite/ar/ViewDetails?ID=31728

which specified 2018-03-24 (Saturday) and 2016-03-26 (Saturday). None of
the decrees specify a time, and in the earlier two years tzdata uses 01:00.

Either the Palestinian cabinet has changed its practice and is now
switching Fridays at some time ([a] 01:00? [b] 24:00?) or they did not
actually change practice and their decree is intended to mean 2019-03-29
(Friday) at [c] 25:00, i.e. 2019-03-30 (Saturday) at 01:00; ... or we
got the data wrong in previous years and nobody reported it.

If the correct answer is [c] then tzdata 2019a is OK as-is. If it is [a]
or [b] or something else, we should fix tzdata and issue a 2019b.

The Ramallah News URL https://ramallah.news/post/123610 that is cited in
tzdata no longer works (in any of the three forms cited in drafts); it
now gives a 404. Of the two other URLs Even Scharning mentioned,
http://palweather.ps/ar/node/50136.html says "Daylight saving time is
due to start on Saturday, March 30, and the clock is to be presented at
midnight on Friday" [Google translation], and http://pnn.ps/news/401130
says "Summer time is due to begin on Saturday, March 30, and the clock
will start at 60 minutes at midnight on Friday" [Google translation].

Given all this above, a plausible answer is [b] and the attached
proposed patch implements [b] and guesses a similar pattern in future years.

It would be nice to get a reliable confirmation of this, though. Plus,
it'd be nice to know whether the practice will change this fall, too.
Perhaps someone who writes Arabic could email the relevant cabinet
contact and mention the issues Matt describes in
<https://codeofmatt.com/on-the-timing-of-time-zone-changes/>.