Add information about how H2O handles date columns to the user guide

[exalate-issue-sync]

Not sure the best place to add this, either in the import data section or the data manipulation section (or both).

Info:

H2O represents dates as (unix) timestamps - these are then raw input to the algorithm, this is not very useful in most cases; user is expected to do their own feature engineering and break the data into day, month, year, ... using the functions H2O provides

[h2o-ops]

JIRA Issue Details

Jira Issue: PUBDEV-8595
Assignee: hannah.tillman
Reporter: Erin LeDell
State: Resolved
Fix Version: 3.36.1.1
Attachments: N/A
Development PRs: Available

[h2o-ops]

Linked PRs from JIRA

#6084