A recuring question in the last 3 months has been: how many dates do we need ?

In ERP5, we use:

• start_date for the date something begins (ie. shipping)
• stop_date for the date something finishes (ie. shipment arrival)

We also have:

• creation_date
• modification_date
• and possibility tons of other dates related to edit_workflows of documents

As well as:

• effective_date for begin of publication
• expiration_date for end of publication

So, we wondered, what was a birth date ? Or, if one prefers, is there any other date which we should add to our properties.

We found one case:

• a Sale Order (start_date, stop_date, etc.) uses all the above dates
• and requires two more dates probably: the date the order was created by the customer, not the date it was created in ERP5; the date the order is no longer valid according to the customer. So we though about begin_date and end_date

We found other cases

• a document with 8 dates to define a list of standard date ranges related to holidays

At this point, the recommened approach is

• use start_date, stop_date, publication dates and workflow based dates
• if you need more, create ad-hoc dates which are customer specific if possible

This will save hours of discussion to decide if one should use start/stop or begin/end and force unification.

There is another date-alike property present only in the SQL catalog which represents on each object the latest date at which it was indexed from SQL server point of view (ie, the date is completely handled by the SQL server, it's not the date of the zope server if they are on distinct machines). The purpose is to be able to reindex a set of objects which were recently indexed when a backup restoration happens (and restored zodb is older than restored catalog) without having to reindex everything.