datedatetimeexpressionqgis
I would like to calculate the number of days between two dates. The first date is written in attribute table [YYYY-MM-DD] (creation date) and the second is today [now()]. The goal is, to get the age of every feature.
I need it as QGIS expression to create a virtual field.
date1 (attribute in table) - now() = age (as virt. field)
Pretty sure this is what you are looking for:
Simplify Date and Time Calculations
Calculating a Past or Future Date If your features have a single date and time, and you need to calculate a second date or time relative to the first, use the DateAdd function. It adds or subtracts a specific interval from the original date and returns the resulting second date.
You can use the following code which connects the attributeValueChanged event to a function we can define which inserts the results of the $now expression. Highlight your layer and copy/paste the following into the Python Console:
layer = qgis.utils.iface.activeLayer()
def update():
field = layer.fieldNameIndex('mod')
e = QgsExpression( " $now " )
e.prepare( layer.pendingFields() )
for feat in layer.selectedFeatures():
feat[field] = e.evaluate( feat )
layer.updateFeature( feat )
layer.attributeValueChanged.connect(update)
Select the feature by clicking the row number (shown in the red box in the image) or from the map canvas and edit any attribute for that feature. The attribute in your mod field should update:
Note: I used a string field instead of date in order to get the time, otherwise the date field only records YYYY-MM-DD.
Best Answer
You can compute the duration between the two dates using the
agefunction. Since it returns a timespan, you can then extract the number of days from it.