Testing results and notes for FAT32 and exFAT drive timestamps on Linux.

Recent Linux exFAT status => https://github.com/relan/exfat/issues/38
The version installed by Ubuntu appears to handle simulated DST rollovers, 
but not timezone changes.

All resuls are versus files on a linux local drive, whose times change on 
tz change only.  The system was not rebooted before some tests (though 
it might not be in practice either).

*reboot*

timedatectl set-local-rtc 0 (recommended by Linux)
   initially
	fat32	off by -8 hours
	exfat	agrees with linux local drive

   set time+date and wait for DST (post reboot or not)
	local	unchanged
	fat32	still off by -8 hours (unchanged)
	exfat	agrees with linux local drive

   set timezone only
	local	plus one hour
	fat32	off by -1 hour from linux local drive
	exfat	off by -1 hour from linux local drive

   set date in future post DST
	(after resetting intial time, date and tz: fat32 now agrees with linux local; why?)
 	fat32	agrees
	exfat	agrees
	after rebooting, fat32 is -8 hours off, exfat agrees

*reboot*

timedatectl set-local-rtc 1 (not recommended, but useful on dual-boot systems)
   initially
	fat32	agrees
	exfat	agrees

   set time+date and wait for DST (post an extra reboot or not)
	local	unchanged
	fat32	agrees
	exfat	agrees

   set timezone only
	local	plus 1 hour
	fat32	off by -1 hour from linux local drive
	exfat	off by -1 hour from linux local drive

   set date in future post DST
 	fat32	agrees
	exfat	agrees


Related quotes from the web and man pages:

"""
To avoid problems with time zone and DST switching, it is recommended to keep 
the hardware clock in UTC. The shown Example 2.11, Synchronizing the Hardware 
Clock with System Time is useful, for example, in case of a multi boot with a 
Windows system, which assumes the hardware clock runs in local time by default, 
and all other systems need to accommodate to it by using local time as well. 
It may also be needed with a virtual machine; if the virtual hardware clock 
provided by the host is running in local time, the guest system needs to be 
configured to use local time, too. 
"""

"""
 set-local-rtc [BOOL]
           Takes a boolean argument. If "0", the system is configured to
           maintain the RTC in universal time. If "1", it will maintain the
           RTC in local time instead. Note that maintaining the RTC in the
           local timezone is not fully supported and will create various
           problems with time zone changes and daylight saving adjustments.
           If at all possible, keep the RTC in UTC mode. Note that invoking
           this will also synchronize the RTC from the system clock, unless
           --adjust-system-clock is passed (see above).
"""

"""
If you have multiple operating systems installed in the same machine, they 
will all derive the current time from the same hardware clock: for this reason
you must make sure that all of them see the hardware clock as providing time 
in the same chosen standard, or some of them will perform the time zone 
adjustement for the system clock, while others will not. In particular, it is
recommended to set the hardware clock to UTC, in order to avoid conflicts 
between the installed operating systems. For example, if the hardware clock 
was set to localtime, more than one operating system may adjust it after a 
DST change, thus resulting in an overcorrection; more problems may arise when 
travelling between different time zones and using one of the operating systems 
to reset the system/hardware clock. 
"""