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Time Standard Measurement Standard may refer to:
The International System of Units (SI) definition of the second, the primary global time unit used in scientific measurement.
A continuous atomic timescale maintained by timing laboratories, used as a basis for international timekeeping.
The primary civil time standard used worldwide, derived from atomic timescales and adjusted with leap seconds.
The time reference used by the GPS system, based on atomic clocks and defined to align with civil time conventions.