A lot depends on how you plan on looking up times? Personally, I'd use a lightweight database, like DBD::DB_File, so that I can offload all my date arithmetic to something that does it, and does it correctly (and fast). Thus, your question could be reworded (using SQL) as 
SELECT pressure
   FROM baro_over_time
 WHERE time_measured < ?
 ORDER BY time_measured DESC

[download]
Then, the first value returned is the one you want. (Since the values are in descending order, the last measurement before the time specified is the first one returned.)

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In reply to Re: Data structure advice by dragonchild
in thread Data structure advice by robinbowes

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