A new Geologic Time Scale (GTS2004) is presented, integrating current stratigraphic and geochronologic data. Key features, construction methods, and future improvements are outlined. The accompanying International Stratigraphic Chart shows the current chronostratigraphic scale with age uncertainties. Special attention is given to the Precambrian and Neogene, which have achieved high precision. The scale is based on relative time units, with global reference points defining boundaries. The Precambrian is formally classified chronometrically, but this is being challenged. The Neogene has been orbitally tuned with 40 kyr accuracy. The scale integrates various techniques depending on data quality. The construction involved specialists from different fields, including geochemists, stratigraphers, and geomathematicians. The scale uses radiometric dates, astronomical tuning, and statistical methods to estimate uncertainties. The Precambrian time scale is currently flawed and needs redefinition based on the rock record. A "natural" time scale is proposed, using stratigraphic events and calibrated with multiple geochronometers. The Neogene time scale is highly detailed, with an accuracy of 1–40 kyr. The GTS2004 replaces the previous International Stratigraphic Chart and includes new data. Future challenges include defining all Phanerozoic stage boundaries, orbital tuning of polarity chronos, and resolving zircon controversies. The next version of the Geologic Time Scale is planned for 2008. The authors are leading experts in stratigraphy and geochronology, with contributions from various institutions. The scale aims to improve understanding of Earth's history through precise, standardized time divisions.A new Geologic Time Scale (GTS2004) is presented, integrating current stratigraphic and geochronologic data. Key features, construction methods, and future improvements are outlined. The accompanying International Stratigraphic Chart shows the current chronostratigraphic scale with age uncertainties. Special attention is given to the Precambrian and Neogene, which have achieved high precision. The scale is based on relative time units, with global reference points defining boundaries. The Precambrian is formally classified chronometrically, but this is being challenged. The Neogene has been orbitally tuned with 40 kyr accuracy. The scale integrates various techniques depending on data quality. The construction involved specialists from different fields, including geochemists, stratigraphers, and geomathematicians. The scale uses radiometric dates, astronomical tuning, and statistical methods to estimate uncertainties. The Precambrian time scale is currently flawed and needs redefinition based on the rock record. A "natural" time scale is proposed, using stratigraphic events and calibrated with multiple geochronometers. The Neogene time scale is highly detailed, with an accuracy of 1–40 kyr. The GTS2004 replaces the previous International Stratigraphic Chart and includes new data. Future challenges include defining all Phanerozoic stage boundaries, orbital tuning of polarity chronos, and resolving zircon controversies. The next version of the Geologic Time Scale is planned for 2008. The authors are leading experts in stratigraphy and geochronology, with contributions from various institutions. The scale aims to improve understanding of Earth's history through precise, standardized time divisions.