12 hours after death rigor mortis reaches maximum stiffness and your body becomes the most stiff.
Rigor mortis refers to the state of a body after death, in which the muscles become stiff. It commences after around 3 hours, reaching maximum stiffness after 12 hours, and gradually dissipates until approximately 72 hours after death.
As the flow of blood ceases, anaerobic metabolism leads to the formation of lactic acid and the soft, pliable muscle becomes stiff and rigid.
If meat is hung in a cool place for a few days ('conditioned'), the meat softens again.
For approximately the first 3 hours after death the body will be flaccid (soft) and warm.
After about 3-8 hours is starts to stiffen, and from approximately 8-36 hours it will be stiff and cold.
The body becomes stiff because of a range of chemical changes in the muscle fibers after death.
For bones to turn to dust it takes around 100 or more years.
Your bones would certainly be turned to dust in around 1000 years or more.
Even when a body is embalmed and in a coffin the body eventually decomposes fully and nothing is left and even the coffin may be decomposed or rusted or corroded away depending on the material the coffin is made of.
The time it takes for a body to fully decompose depends on if the body is exposed to the air, in a coffin, has been embalmed etc.
For a body that is not embalmed and exposed to the air the body can fully decompose in a few weeks to a month or two months depending on the conditions.
In a coffin a non embalmed body can take a year or 2 years or so before the body fully decomposes.
For an embalmed body in the coffin it can take 10 years or even 20 years or more for the body to fully decompose.
By 50 years in, your tissues will have liquefied and disappeared, leaving behind mummified skin and tendons.
Eventually these too will disintegrate, and after 80 years in that coffin, your bones will crack as the soft collagen inside them deteriorates, leaving nothing but the brittle mineral frame behind.
In a temperate climate, it usually requires three weeks to several years for a body to completely decompose into a skeleton, depending on factors such as temperature, humidity, presence of insects, and submergence in a substrate such as water.