The Miyota caliber 0S30 is a quartz chronograph watch movement. You might also see other listings incorrectly refer to this movement at OS3O, but is should be zero-S-3-zero not O.
Miyota claims the accuracy of this movement to be +/-20 seconds/month.
Resetting the chronograph to zero
If your chronograph hand is not resetting to 12:00 or “zero” position, then you can try the following steps:
Pull the crown to position 2
Press button A to advance the chronograph hand forward until it is lined up with 12:00. If you long-press A, the hand will move forward faster.
Push the crown back to position 0
Note: if you push the crown back in to position 0 while the chronograph hand is still advancing forward, then it will stop the chronograph hand and recognize it as zero position. In this case, you will have to start over again.
Changing the Battery
The Miyota caliber 0S30 takes an SR927W (395) battery cell. Miyota states that the estimated battery life is around 5 years. Keep in mind that this is with the chronograph function off. If you use the chronograph daily or leave it running constantly, the battery will drain faster due to the extra energy needed to drive the gears for the stopwatch and elapsed time counters.
To change the battery, the cell slips under a tab (near the + icon) and is held in place by another tab on an arm that flexes slightly. Gently use your tool to slide this arm/tab aside and the battery will pop up. Wedge the new battery under the permanent tab, hold the spring tab aside, press the cell down and let the spring tab return to its place which holds the battery down.
The average replacement price at the time of this post was from $27.95 – $32.95.