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https://issues.apache.org/jira/browse/DRILL-262?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13792018#comment-13792018
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Julian Hyde commented on DRILL-262:
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At the user level, I'd recommend that Drill supports DATE, TIME and TIMESTAMP.
Later it can support TIME WITH TIMEZONE and TIMESTAMP WITH TIMEZONE types.
How these are represented internally is much less important.
> Implement support for DATETIME and TIMESTAMP types
> --------------------------------------------------
>
> Key: DRILL-262
> URL: https://issues.apache.org/jira/browse/DRILL-262
> Project: Apache Drill
> Issue Type: Task
> Reporter: Ben Becker
>
> Many functions and operators in Drill need to handle DATETIME and TIMESTAMP
> types. This may require two formats; the most important of which is an
> expanded format for use during processing:
> {code}
> struct pg_tm
> {
> int tm_sec;
> int tm_min;
> int tm_hour;
> int tm_mday;
> int tm_mon; /* origin 0, not 1 */
> int tm_year; /* relative to 1900 */
> int tm_wday;
> int tm_yday;
> int tm_isdst;
> long int tm_gmtoff;
> const char *tm_zone;
> };
> {code}
> Note that:
> - Fractions of seconds are stored in an auxiliary 32-bit integer (thus
> internal time functions usually take both pg_tm and fsec_t arguments).
> - Resolution is guaranteed to the microsecond, with a date range of 4713 BC -
> 294276 AD.
> - MySQL stores datetime values as simple unix time format (second resolution,
> 1970 - 2038 date range)
> In Postgres, the TIMESTAMP type is encoded into 64 bits for storage as
> follows:
> - The date portion is packed in the upper 28 bits as the delta of years,
> months and days since postgres epoch (1/1/2000).
> - The time portion is packed in the lower 36 bits as hours, minutes, seconds
> and fsecs (fractions of a second).
> - The specific encoding logic can be found in
> {{src/backend/utils/adt/timestamp.c}} in {{tm2timestamp()}}, {{date2j()}} and
> {{time2t()}}.
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