How to adjust the band on a GW800D Tough Solar

Take it to a local jeweler to replace the back up battery.

https://www.fixya.com/support/r27181038-changing_watch_batteries

https://www.google.com/search?q=solar+Gw-8100+battery

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Today my 6-year old Waveceptor has adjusted itself to daylight Savings time without my intervention. I was agreeably surprised. For all the years I have had the watch, I kept the module manual by my side just for the two times a year I have to adjust the time.
All this to tell you that you imperatively have to read the module's manual. If you do not have it visit the Casio Worldwide web site and download it. You need the module number. You will find it on the back of the watch. It is a 4-digit number inside a rectangle.

try this link > http://www.watch-band-center.com/watchstrap-s1237h243-CASIO-Straps-Metal.html

You can get instructions from the Casio web site.

Go to the casio web site "casio.com".

Select "support" and the "manuals",
watches;

Accept terms

Select "watch manual archive"

Read the number of the back of your watch and enter it into the search box

I had a casio and the method was; press the mode button until the display says "HS", then press the 2 or 4 o'clock buttons to adjust the hands to match the digital time; then press mode button until normal operation is achieved.

My watch was a different model to yours, so if this does not work, then you can get
instructions from the Casio web site.

Go to the casio web site "casio.com".

Select "support" and the "manuals",
watches;

Accept terms

Select "watch manual archive"

Read the number of the back of your watch and enter it into the search box

Click on my profile (escapement), then click on Tips and Tricks. There you will find links to all watch manuals. Rate me, please .

Read my tips and tricks. Watch band is called bracelet as well.

Copy the manual from;

http://ftp.casio.co.jp/pub/world_manual/wat/en/qw2688.pdf

Did you try to find solution here?:

http://world.casio.com/wat/download/en/manual/

Rate, please.

That blinking is to let you know: time to change the battery.

Rate me, please.