How to adjust the time of casio g-shock 150a - Casio G-Shock Analog Digital Watch GA-150A-4A GA150A

"G-Shock WR20BAR" could mean hundreds of different G-Shock models. If yours is an all digital G-Shock, the answer is fairly simple. When looking at the watch face, the upper left corner button is the "ADJUST" button. Press and hold the ADJUST button for a couple of seconds. You should start to see something flash on the display. Some models will have many options to select in ADJUST mode. To scroll through them, press the MODE button, which is in the lower left corner. You set the hour, minute, seconds, month, date, and year each separately. When you are done, press the ADJUST button again and you'll be back to normal time keeping.

If you want to learn more about your G-Shock, there is something called a "MODULE" inside it that is the brains of the watch. You can find that on the back of the watch, outlined in a rectangle. Usually a 4 digit number. You can download the manual for your watch using that number, if you enter it on a CASIO website:
http://support.casio.com/en/manual/manuallist.php?cid=009

Watch Archive Casio User Manuals

go here to get manual > http://www.gshock.com/support/

Sounds like you're set for the wrong time zone, and your 12h/24h setting is off.

To change time zone: Hold down the adjust button until it beeps. Your time zone will be flashing at the bottom of the display. Use the Time Memo and/or Receive buttons to change it to the correct time zone. Then... To change to 12H mode: Press adjust again. 12H or 24H will be flashing at the bottom. Use the receive button to cycle the mode. When it's what you want, press adjust once more.

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 "search" and the download your instructions.

If your watch is Casio:

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

If not, give ALL the details.

Rate, please.

Follow this link and get all the info:

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

Rate me, please.

I have A Casio G- Shock, Can't remember how to set the time!!

Press Adjust and hold until blinking city appears.
Press Mode until DST appears flashing.
Press Recieve until mode that you want appears ON OFF AUTO
Press Adjust until not blinking city code.

You most likely don't have the Daylight Savings Time (DST) set to AUTO mode. Just hold the ADJUST button until the time starts blinking. Then hit MODE and DST will show on the top. Hit RECEIVE as needed until you see AUTO in the bottom. Then just hit ADJUST 2 more times and you're set.

These instructions are actually for my Casio G-Shock MTG-900 but I imagine they're very similar for most G-Shock atomic watches.