You have a problem with your rowkeys, if you hash the date you won't be able to use it as a start/stop row for your scans.
Your rowkeys should be something like this:
[16B_schema_MD5_hash][8B_long_timestamp][8B_pkid]
Which you can query like this:
Scan myScan = new Scan(
Bytes.add(Bytes.toBytes(schemaNameMD5Hash), Bytes.toBytes(startTimestamp)),
Bytes.add(Bytes.toBytes(schemaNameMD5Hash), Bytes.toBytes(stopTimestamp))
);