Why did the Nazgûl drop Merry in Bree?

[Gordis]

A piece of bad (?) news: in the "Long-expected party" the times are GMT without extra hour:

At other times there were merely lots of people eating and drinking - continuously from elevenses until six-thirty, when the fireworks started.LOTR, Ch.1

Naturally the fireworks started after sunset.

The sunset for September 22 2009 is 5:59PM without BST
The sunset for September 12 2009 is 6:22PM without BST

Now in the draft written around 1938, before the application of BDST, the time of firewoks was 6 PM, later it was corrected to 6.30.
I guess this change was due to the fact that Tolkien had calculated the difference between Shire calendar and normal calendar.

Uh-oh...