a-series and b-series absolute time and space albert einstein anthropic principle arguments for eternity arrow of time astrarium astronomical chronology astronomical year numbering atomic clock atomic nucleus atomic orbital b-theory of time barycentric coordinate time barycentric dynamical time black hole thermodynamics calculating the day of the week calendar calendar era carpe diem causal sets causal structure causality century chronicle chronobiology chronology chronometry chronon circadian rhythm civil time classical hamiltonian quaternions classical mechanics clock compact space continuous signal coordinate system coordinate time coordinated universal time cosmological decade day daylight saving time days of the week decade deep time digital object identifier dimension discrete time dominical letter dreamtime duration edgar allan poe electron endurantism epact ephemeris time equation of time equinox eternal return eternity euclidean space euler characteristic fictitious force flux fortnight four-vector four dimensionalism fourth dimension frame-dragging frame of reference future futurology galactic year galilean transformation general relativity geocentric coordinate time geochronology geodesic geologic time scale geological history of earth gravitational time dilation greenwich mean time gregorian calendar helix hermann minkowski hexadecimal time history history of timekeeping devices horology hour hourglass immanuel kant immortality intercalation international atomic time international commission on stratigraphy international date line international earth rotation and reference systems service inverse-square law islamic calendar julian calendar kalachakra latitude leap second leap year light light cone local spacetime structure long now foundation longitude loop quantum gravity lorentz lorentz transformation lunar calendar lunisolar calendar lustrum m-theory manifold marine chronometer mathematical model mathematics of general relativity max tegmark measurement mental chronometry metric space metric time metrology millennium minkowski space minute month newtonian time in economics nuclear time scale orbit partial differential equation particle accelerator past paul ehrenfest penrose-hawking singularity theorems perdurantism periodization philosophy of space and time photon physical cosmology physics planck epoch planck scale planck time planet present prime meridian proper time prophecy proton quantum mechanics radio clock radius reaction time real number rectilinear regnal year relativity of simultaneity saeculum second sense of time sidereal time solar calendar solar time solstice space space shuttle spacetime symmetries spacetime topology special relativity specious present speed of light spherically symmetric spacetime star static spacetime stationary spacetime string theory sun sundial system time t-symmetry temporal finitism temporal parts tempus fugit terrestrial time the time machine the unreality of time theoretical physics theory of relativity three-dimensional space time time-based currency time banking time capsule time dilation time discipline time domain time in physics time offset time signature time standard time travel time use research time value of money time zone timekeeper timeline tropical year units of measurement universal time universe velocity watch water clock wave week wheel of time wikibooks william rowan hamilton world line year