Days

Every three minutes is a day in nend.io, with the 10th day being the highest day in almost all player's lives. At the start of each new day the player has the option of upgrading one of their skills, and at day 7, the player begins to visibly age. You can tell what day it is by checking in the bottom left hand corner. In addition, every time a day passes, a rectangle pops up near the day indicator showing day numbers from 1-9, a death icon, and Death, in black clothes, holding a scythe (in order from left to right).

Day 0
Every player spawn on day 0, with part of the day already being over. When you spawn, you do not have the choice of upgrading any skills, but you will at day 1, and at the start of every new day. Each new day starts when the white box in the bottom left hand corner completely encloses the blue box containing the day number.

Day 7
The player's appearance does not change until Day 7, when their hair becomes gray and they start carrying a cane (the cane is not a physical item, just a cosmetic one). It is possible to change your hair back to normal for the rest of your life (until you die) by going to a hairdresser and getting a haircut. Also, after this day an icon pops up on the screen (on top of the other ones pointing you towards offices and dormitories), pointing you towards the nearest Nursery (where you purchase your baby).

Day 10
At day 10, most player's lives end. This is because you begin to constantly lose health, quickly killing you after half of a minute. If you do end up dying, you will either lose everything and have to restart, or you will respawn as a baby, with everything other than what was in your inventory. For the second option to work, you must first purchase a baby (see Babies for more details) at a Nursery.

Life After Day 10
Although most players do not live past day 10, you can technically live on forever. All you have to do is buy health pack after health pack, and heal yourself whenever your health nears 50%. To do this, you must either be inside or in close proximity to a pharmacy that sells health packs. You will still be able to upgrade your skills when you reach the end of the day, meaning it is possible to max out all of your skills. But because each health pack costs 150-250 dollars, you will have to own a lot of property, or you will quickly run out of money. Also, you must be at a pharmacy that is close to a supermarket, since your Food stat will still decrease (unless you are willing to let it run out and you buy more health packs).

Tips/Suggestions
Further Information: Strategies 

It is best to buy your baby (if you want to respawn) at day 7 or 8, since buying a baby, a toy, and giving said toy to your baby can take a day or longer. Also, it is not a good use of your time to try and live past day 10, since buying and using health packs will take up all your time. Instead, buy a baby and let yourself die.