+ Formerly it was said that 'life is what heaven has decided, nothing changeable.' Though, truthfully, many may know when they die, it is possible that they can recognized strange signs within their body as of experience of thousand years ago. We can partly recognize some alerting signs of the dying time of a relative, especially the aging.
Appearance: look if eyes are still keen or dull, chin shrank, dark lips, end tongue withdrew inner...
Body temperature: limbs cooling down gradually.
Heart beats very soft, sometimes there is no circulation, urging breath, now strong, now weak...
Being sick for long while, suddenly becoming healthy, controlled in a strange way. This event is named 'Yin returning' and this is a sign like a candle about to run out of its fuel, just flashing to quench forever.
Denying food or eating just a bit. Legs are gradually extended straight (when dying, legs often are straightly extended)
+ Depending the health of each person, time of dying can last long or short. Moreover if those whose inner mind is without any thoughts, they go away very smoothly and in the contrary if there is something to worry about (failing to meet relative or some business undone) thus because of regret, time of dying can last very long.