The earth is not dated by carbon 14. C14 has a short half life of 5730 years so is only suitable for dating carbon containing objects up to about 60,000 years old. C14 dates are calibrated by tree-ring dates and tree ring dates go back about 12,000 years. Carbon 14 is produced all the time in the upper atmosphere and is the only short half-life isotope. All the other short half-life isotopes decayed completely a long time ago.
Older objects need to be dated by other methods and there are many of them. Three of them, potassium/argon, argon/argon and uranium series dating use the decay of isotopes with long half lives. Potassium 40, for instance, which decays to Argon 40, has a half life of 1.3 billion years. The atomic clock is set, as it were, by volcanic eruptions which means that volcanic tuff and other ejecta can be dated very accurately.