Introduction
This manual provides detailed instructions for the operation and maintenance of your Casio AQ-S820W Series AQS820W-1AV Black watch. Please read this manual thoroughly to ensure proper use and to fully utilize all features of your timepiece. Keep this manual for future reference.

Image: Front view of the Casio AQ-S820W Series AQS820W-1AV Black watch, showcasing its analog-digital display and robust design.
Key Features
- Solar Powered Functionality: Equipped with Tough Solar technology, this watch charges from sunlight or indoor light, storing power for months of use without exposure to light. A built-in power indicator helps track charge levels.
- 100M Water Resistance: Built for active lifestyles, this watch withstands water exposure from rain, splashes, and swimming. Suitable for recreational water activities while maintaining full analog-digital functionality.
- Multi-Feature Display: Analog hands display hours and minutes while the digital screen shows time, date, and additional modes. Includes dual time for tracking two time zones and 31 time zones for world time convenience.
- Auto-Stopwatch, Timer & Alarms: Features a 1/100-second stopwatch, countdown timer, and multiple alarms to keep track of activities, events, and intervals. Includes an hourly time signal for additional scheduling accuracy.
- LED Light & Durable Build: Amber LED backlight with afterglow offers clear visibility in low light. Resin case and band provide comfort, lightweight wear, and resistance to everyday impacts. Resin glass resists scratches.
Setup Guide
1. Initial Charging
Upon first use or after prolonged storage in darkness, expose the watch face to bright light (sunlight is ideal) for several hours to ensure a full charge. The power indicator on the digital display will show the current charge level. Avoid placing the watch in direct sunlight for extended periods in extremely hot environments to prevent damage.
2. Setting the Home City and Time
- In the Timekeeping Mode, hold down the ADJUST button (top left) until the city code starts to flash on the digital display. This indicates the setting mode.
- Use the SEARCH button (bottom right) and LIGHT button (top right) to select your desired Home City code.
- Press the MODE button (bottom left) to cycle through other settings: DST (Daylight Saving Time), 12/24-hour format, seconds, hour, minute, year, month, day.
- Use the SEARCH and LIGHT buttons to adjust the flashing value.
- Once all settings are correct, press the ADJUST button to exit the setting mode. The analog hands will automatically adjust to match the digital time.
Operating Modes
The MODE button (bottom left) is used to navigate between the different operational modes of the watch.
1. Timekeeping Mode
Displays the current time and date. The analog hands show the hour and minute, while the digital display shows the day of the week, month, and day, along with the digital time. To switch between 12-hour and 24-hour format, enter the time setting mode as described in "Setting the Home City and Time" and adjust the 12/24H setting.
2. World Time Mode
Allows you to view the current time in 31 time zones (48 cities). Press the MODE button to enter World Time Mode. Use the SEARCH button to scroll through different city codes. The digital display will show the current time for the selected city.
3. Stopwatch Mode
Measures elapsed time with 1/100-second accuracy. Press the MODE button until "STW" appears. Use the SEARCH button to start and stop the stopwatch. Press the ADJUST button to reset to zero while stopped.
4. Countdown Timer Mode
Functions as a countdown timer, useful for various activities. Press the MODE button until "TMR" appears. To set the countdown time, hold ADJUST until the time flashes, then use SEARCH and LIGHT to set the desired hours, minutes, and seconds. Press ADJUST to confirm. Use SEARCH to start and stop the timer.
5. Alarm Mode
The watch features 5 daily alarms and an hourly time signal. Press the MODE button until "ALM" appears. Use the SEARCH button to cycle through alarms (AL1 to AL5) and the hourly time signal (SIG). To set an alarm, hold ADJUST until the alarm time flashes, then use SEARCH and LIGHT to set the hour and minute. Press ADJUST to confirm. Press LIGHT to toggle an alarm or the hourly time signal on/off.
6. Illuminator (LED Light)
Press the LIGHT button (top right) to illuminate the digital display for easy reading in low-light conditions. The amber LED backlight provides clear visibility.
Maintenance
1. Solar Charging
To maintain optimal performance, regularly expose the watch to light. Avoid blocking the watch face from light sources. A full charge can last for several months in total darkness, but consistent exposure to light is recommended for longevity.
2. Water Resistance (100M)
The watch is rated for 100-meter water resistance, suitable for swimming and showering. Do not operate any buttons while the watch is submerged in water or wet, as this can compromise the water resistance. Avoid exposing the watch to hot water or steam, which can damage seals.
3. Cleaning
Wipe the watch case and band with a soft, dry cloth. For stubborn dirt, use a soft cloth dampened with water and a mild neutral detergent, then wipe dry. Avoid using volatile agents like thinner or benzine, as they may damage the resin components.
Troubleshooting
- Watch is not charging or power indicator is low: Ensure the watch face is exposed to bright light. If stored in darkness, it may take several hours of exposure to sunlight to fully charge.
- Analog hands do not match digital time: After setting the digital time, the analog hands should automatically adjust. If they do not, manually adjust them by entering the time setting mode and following the instructions for hand alignment (refer to the full Casio module manual for specific hand alignment procedures if needed, as this model typically auto-adjusts).
- Buttons are unresponsive: Ensure the watch is not in a locked mode (if applicable, though this model typically does not have a button lock). If the battery is extremely low, some functions may be restricted. Charge the watch fully.
- Incorrect time or date: Re-enter the Timekeeping Mode settings and verify your Home City, DST setting, and current time/date.
Specifications
| Feature | Detail |
|---|---|
| Model Number | AQ-S820W-1AVCF |
| Power Source | Tough Solar (Solar Powered) |
| Water Resistance | 100 meters (10 BAR) |
| Display Type | Analog-Digital |
| Light | Amber LED Backlight with Afterglow |
| World Time | 31 time zones (48 cities + UTC), daylight saving on/off |
| Stopwatch | 1/100-second, measuring capacity: 23:59'59.99'' |
| Countdown Timer | Measuring unit: 1 second, countdown range: 1 minute to 24 hours |
| Alarms | 5 daily alarms, hourly time signal |
| Case/Bezel Material | Resin |
| Band Material | Resin |
| Glass Material | Resin Glass |
| Dimensions | 4.57 x 3.46 x 2.91 inches (Package) |
| Weight | 5.5 ounces (Package) |
Warranty and Support
Your Casio watch is covered by a manufacturer's warranty. Please refer to the warranty card included with your purchase for specific terms and conditions, including warranty duration and coverage details. For technical support, service, or inquiries regarding your watch, please contact Casio customer service through their official website or the contact information provided in your warranty documentation.





