• Measure of Time

• क्ष ( continuously dissipating )
  • क्षण ( time )
    • क्षणाणु

Chronometry[a] or horology[b] (lit. 'the study of time') is the science studying the measurement of time and timekeeping.[3] Chronometry enables the establishment of standard measurements of time, which have applications in a broad range of social and scientific areas. Horology usually refers specifically to the study of mechanical timekeeping devices, while chronometry is broader in scope, also including biological behaviours with respect to time (biochronometry), as well as the dating of geological material (geochronometry).

Horology is commonly used specifically with reference to the mechanical instruments created to keep time: clocks, watches, clockwork, sundials, hourglasses, clepsydras, timers, time recorders, marine chronometers, and atomic clocks are all examples of instruments used to measure time. People interested in horology are called horologists. That term is used both by people who deal professionally with timekeeping apparatuses, as well as enthusiasts and scholars of horology. Horology and horologists have numerous organizations, both professional associations and more scholarly societies. The largest horological membership organisation globally is the NAWCC, the National Association of Watch and Clock Collectors, which is US based, but also has local chapters elsewhere.

• AD
• BC
• second
• day = ( 24 hrs )
• era
• millenium
• decade

• Calender
• Era
• Definite Age

• Spatio-temporal frames
  • Time and Relative motion in space
    • velocity , speed ( meter per second )
  • Time and Relative position in space
  • Time and Relative Substance in space
    • half life
  • Time and relative life in space
    • definite age
      • definite lifetime
      • definite earth time
      • definite universe time