I am sure no one has thought of this….I first realized it when I had mehendi the day before the engagement of a friend’s daughter. I didn’t intend it to,but it got on my nails. I rather liked the effect, and then I applied mehendi again just before I left for the US. Each date is thus marked on my growing nails, and the mark before the engagement was clipped off….just before I applied the mehendi for the same young woman’s marriage! So the passage of time is there to see on my fingernails….