Watch Related Terms & Terminology

Term Definition
Mean Solar Day

The average, taken over one year of all the true solar days.


An imaginary line on the earths surface passing North – South in relation to the polar axis. In 1884, the 0 meridian was fixed as a line passing North – South through Greenwich Observatory in England.


Self compensating balance spring alloy, basically nickel steel containing beryllium and other additions.


Motion of balance from one position of maximum displacement to the next and the return to original position.

Perpetual Calendar

Indicates the day of the week, the date, the month and the phases of the moon and Automatically allows for varying lengths of months, as well as leap years – No manual correction is necessary.

Point Of Attachment Springing

To a watchmaker, this expression means the point of attachment of the balance spring to the collet is located in the most favorable position to ensure good performance in the vertical positions.


Watchmakers say that a balance is “in poise” when the balance is in neutral equilibrium, as verified on the poising tool for example. Its significance is that the center of gravity lies on the axis of rotation.

Positional Error

Difference between the rates of the watch in various positions.


A timer or chronograph with a graduated dial or bezel used to indicate the number of heart beats per minute. This is done by measuring the time taken for a fixed number of beats to occur.


Crystalline silica; under certain conditions, pieces cut from quartz crystals can be maintained in rapid oscillation of very stable frequency. For this reason they are used in clocks, timing machines & many other applications.


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