Definitely won't be an easy task if your not familiar with micro's
I'm not sure if you wanted a remote logger or a local one that is permanently connected to the PC, but the previous posts kind of suggest that it is a remote device
**broken link removed** (time & date IC) with your micro would probably give a lot better results, but its dependent on the quality of the crystal and the circuit layout. 1 minute a month is definitely achievable as ericgibbs has managed
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From there you can get time and date stamps fairly easily. Storing this data into EEPROMs is the next hassle, given the amount of data, the PIC's on board memory won't be suffice..
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**broken link removed** of using multiple EEPROM's with I2C. Each device contains 32K x 8 (256 Kbit) of memory.
Each data packet would contain: Hour, Minute, Month, Day, Year, Sample information. Given that all other samples except the Sample are bytes (sample would most probably be a Word result - 16bits) then each packet of info would be 7 Bytes.
A single 32Kbyte eeprom could store 4571 tagged samples, but in a year there are 365 * 24 * 60 minutes (525600).
One solution would be to use a more expensive data storage solution (bigger eeprom), another is to refine your method of storing data, eg, only store the Time/Date at the start of each EEPROM in use, from there each sequential stored sample is 1 minute from the last... Your "downloading" software on the PC would recognize this and know how to treat the following information - greatly improving your storage capabilities.
Perhaps a mix of both methods would suite your application