how to get lost file if Time Machine merge dates?

[nova]

I observe a strange behaviour of Time Machine.

Let x<y<z be three dates.

I have a file before x and back up at x.
I delete the file y and now it's z. However, I observe that for unknown reason (the backup disk is large enough) Time Machine merge x, y and z.

I must go back the date x to find the file but I can't since I can find things only before x or after z.

What happen to Time Machine????

[bobtomay]

Not strange at all. It is exactly the way Time Machine behaves. From Apple's Time Machine feature page.

Timing is everything.
Every hour, every day, an incremental backup of your Mac is made automatically as long as your backup drive is attached to your Mac. Time Machine saves the hourly backups for the past 24 hours, daily backups for the past month, and weekly backups for everything older than a month. Only files created and then deleted before the next hourly backup will not be included in the long term. Put another way: You’re well covered.

As you can see, the 'y' backups disappear at certain points in time.
You would need phenomenal amounts of storage space to maintain hourly backups even for a year.

[nova]

hmm... if i understand well, when i hope to save as backup a file "forever", the file must exists at least for one month? I thought I was "well" covered not in such sense...