Sonic's World

Mobius is the homeworld of all Mobians, Overlanders and humans and it the primary setting of the Archieverse continuity and Sonic the Hedgehog series. As it turns out, Mobius is actually a future version of Earth (in an alternate dimension). According to this universe's timeline, Earth's year would be approximately 14,016 CE, with Mobius' calendar year at 3237. It is still unknown exactly what was the starting point for their calendar, but its was likely calculated using what the Echidna Tomes call the Days of Fury. (StH: #124, #148)

Prehistoric
During the 21st century, an alien race known as the Xorda came to Earth to offer an alliance to its human population. However, the emissary they dispatched was captured, studied and subsequently dissected by a group of scientists led by Ivan Kintobor, a leading scientist at the time. Ivan had hoped to use the captured alien and its technology to produce the robot Isaac as well as numerous other creations. His methods however proved antagonistic towards the Xorda. In retaliation, the aliens bombarded the planet with Gene Bombs with the intention of exterminating all life on the planet. The bombs had an unforeseen side effect however. The human population underwent a de-evolution, forming the four-fingered Overlanders, which are seen on Mobius today, while the rest of the animal kingdom experienced a rapid evolution, forming modern-day Mobians. (StH: #124, #125)

Beginning of Civilizations
Several decades after the Xorda attack, the planet suffered a massive environmental cataclysm. The Gene Bombs were supposed to preserve Earth's environment as it was when it was attacked. However, their interaction with the planet caused massive volcanic reactions, hurling billions of tons of ash and dirt into the air. This is what is chronicled as the First Day of Fury in Echidna theology. (StH: #148)

The Days of Fury continued to affect Mobius for thousands of years. The Echidna Tomes describe them as "natures way of adjusting to environmental changes it undergoes over a certain duration" according to Athair. Prior to the Day of Fury which happened in the year 3235, Athair stated the last recorded Day of Fury happened some "twelve hundred years ago". (KtE: #12)
 * This may have been during the Coming of the Chaos Emeralds to Mobius, which nearly wiped out all life on the planet, as well as resulting in Mammoth Mogul becoming immortal, when one of the Chaos Emeralds imbedded in his chest. The Coming of the Chaos Emeralds may also have occured during a previous Day of Fury, which happened over 3000 years ago and was the cause for the calendar being reset.

Around the Mobian year 2200 (approximately 11,000 years after the Xorda attacked), the Echidnas established themselves as a technologically superior race above the other species on the planet. While they were already launching ships into orbit and using science for medical cures, the rest of the planet's species were still primitive and caveman-like. (KtE: #12)

Measurements
The Mobian unit of weight is the Stone, which works out to be approximately 4 Kg (8.8 lb). And their measure of height is the Mark, which is about 1.4 cm (a little over 1/2 inch).