:date: 2019-04-03

========================
Wednesday, April 3, 2019
========================

Difference between DurationField and TimeField
==============================================

Should we deprecate :class:`lino.core.fields.DurationField` and recommend using
a TimeField instead?  No. A DurationField is to store a **number of hours (and
minutes)** while a time field contains the time part of a timestamp.  A
duration can be more than 24 hours, or it can be negative. I updated the
documentation about the :mod:`lino.utils.quantities` module. Thanks to `this
discussion on SO
<https://stackoverflow.com/questions/100210/what-is-the-standard-way-to-add-n-seconds-to-datetime-time-in-python>`__.

I noted that :class:`PercentageField <lino.core.fields.PercentageField>`
doesn't use :mod:`lino.utils.quantities`.  This field is currently just a thin
wrapper around :class:`DecimalField`, and Lino adds a percent sign when
printing it.  One day we might change this (:ticket:`2941`).