|Brand:||Seiko, Seiko Instruments Inc.|
|Reserve:||40, 41 hours|
|Winding:||Automatic, Bi-Directional Automatic Winding|
|Diameter:||27.40 mm (12 ligne)|
|Complications:||Bilingual Day Wheel, Date, Day, Hacking Seconds, Hand Winding, Quick Date Correction, Quick Day Correction|
|Hands:||Central Hour Hand, Central Minute Hand, Central Seconds Hand, Date Window at 3:00, Day Window at 3:00|
|Production: 2010 – Current|
Seiko Cal. 4R36A is a mainstream automatic movement with day and date wheels. It is also offered by Time Module Inc. (TMI) as Cal. NH36A for use by other watch makers. It is closely related to the date-only Cal. 4R35.
Cal. 4R36 was introduced around 2010 and used in the Prospex Automatic watches, Model SRP581 and SRP583 around 2014. It is also used in the Seiko Original line, where the company specifies accuracy to -35/+45 seconds per day and 41 hours power reserve.
Note that Cal. NH36A is rated at -20/+40 seconds accuracy while Cal. 4R36A is rated at -35/+45 seconds. Seiko produces Cal. NH36 in a variety of color and date window variations with black text on a white dial and day and date wheels or reversed, and with the day and date at 3:00 or 6:00. Day wheels are available in English/Spanish, English/Arabic, or English/Chinese.
The movement can be manually wound with the crown in position 1. Rotate the crown clockwise to wind the mainspring.
The day and date wheels are advanced with the crown in second position (one notch out). Turn the crown counter-clockwise to advance the date wheel by one day. Turn the crown clockwise to advance the day wheel.
The time is set with the crown in third position (pulled all the way out). Rotate the crown clockwise to advance the minute and hour hands and counter-clockwise to turn them backward.
|Spron 510 Mainspring|
NH71A (skeleton, gilt)
|Day and Date||4R36A|
|Date, 24 Hour Subdial||4R37A|
|24 Hour Subdial||4R39A|
|Date by Pointer|