Hi have the blx-100 and i want to change it back to 12 hour time..how?

Check the caliber code of your watch on the case back and go here
https://www.seikowatches.com/us-en/customerservice/instruction?language=English

SHAKE N WAKE: TO CHANGE TO MILITARY TIME
Hit Mode 3 times to set the time
Hit Reset/TimeSet twice to make hours flash
Now keep hitting StartStop/Adjust repeatedly. After you go through 12 hours of AM then 12 hours of PM it will start going through the hours in military time.

Hi.
I take it that your watch changes date at 12 noon, instead of 12 midnight.
If so change the time of your watch 12 hours, so it reads the same time, but instead of am, it is pm, or visa versa. Analog watches do not have a 24 hour time setting.

Your watch is 12 hours out, as it "thinks" that midnight is midday.

The solution is to wind your watch forward 12 hours and then the date will change at midnight.

Your watch is 12 hours out of step. (The date changes every second revolution of the hour hand.)

Wind your watch forward 12 hours, (you may have to reset the date) and it will then change around midnight.

Hi Harry,

Your Module number is 2271.
1. To set the time, press and hold button A (left top) until Seconds digits start to flash.
2. Press button D (lower left) to move flashing in the following sequence to change other setting:
Seconds >> Hour >> Minutes >> 12/24 Hour Format >> Year >> Month >> Day >> (Then back to Seconds)
3. While a setting is flashing, use E (+) (bottom right) and B (-) (top right) to change it.
Note: When in the 12/24 Hour Mode, use E and B to toggle between 12-Hour and 24-Hour Mode.
4. Press buton A to exit setting screen.
Your time should now be set.

You may also download a manual for watch/Module number:
http://pathfinder.casio.com/resource/manuals/module_2271.pdf

This should give you all the info you need to operate all the functions of your watch. Thanks.

Regards, Bill

NOTE: 12/24 HOUR TIME IS SELECTED BY PRESSING RESET/LIGHT ONLY WHEN THE HOURS MARKER IS 
FLASHING. THE “A” OR “P” WILL DISAPPEAR WHEN THE 
WATCH IS SET TO 24-HOUR TIME. 

hello..this is not abig problem..just a sincronization one...ususlly I set the date around the 12 oclock in the night..the 0 hour..its easier...if you dont want to do this...well..then just count the hours ..remember you have the 24 hours /day..and remember the date is changing in the night around 12 oclock..
for instance...lets say..now you want to set the date..you count the hours until tonight at 12...you put it lets say...with 12 hours back..and wait the change in the midnight..
the easier way is to set it at midnight
oh...by the way..I saw watches which change the date around 2 oclock in the night..but this is a very small %...99% are set to do it at 12..
good luck

quickly press the bottom-left button twice.
then, press the bottom-right button once, and then the top-right button once. this should add 1 to the day. keep pressing the top-right button until u get the right day, the press the top-right button again.

now, how do u change the time format back to twelve hr. ?