Alltime.ini
Cumulus maintains a number of 'all time records' for the station -- highs and lows for many of the readings. These were stored in a database file (alltime.rec) however starting with Build 924 (version 1.8.9) of Cumulus this data is now stored in a text file which can be easily edited if needed.
The first time you run Build 924 or later of Cumulus it will convert your alltime.rec file into an alltime.ini file and use the ini file going forward. The alltime.ini file is located in the 'data' folder
Date, Time and Decimal formatting is as per your regional settings on the PC running Cumulus.
Example line of the file
[Temperature] hightempvalue=22.7999992370605 hightemptime=01/07/2009 14:24:53 lowtempvalue=-7.59999990463257 lowtemptime=24/02/2010 05:19:10 lowchillvalue=-10.60777759552 lowchilltime=28/10/2008 04:40:00 highmintempvalue=14.5 highmintemptime=02/07/2009 09:00:00 lowmaxtempvalue=1.89999997615814 lowmaxtemptime=22/11/2008 08:00:00 [Wind] highwindvalue=64.9000015258789 highwindtime=20/12/2008 00:45:00 highgustvalue=89.0999984741211 highgusttime=20/12/2008 00:45:00 [Rain] highrainratevalue=94.4000015258789 highrainratetime=24/10/2008 21:40:00 highdailyrainvalue=40 highdailyraintime=27/10/2006 08:02:00 highhourlyrainvalue=10 highhourlyraintime=31/10/2006 13:30:00 highmonthlyrainvalue=166 highmonthlyraintime=01/10/2006 [Pressure] highpressurevalue=1044.90002441406 highpressuretime=14/02/2008 10:15:00 lowpressurevalue=948.400024414063 lowpressuretime=31/01/2008 18:51:00