Closes #15618: Always use ISO 8601 date & time formatting (#15737)

* Introduce the isodate(), isotime(), and isodatetime() template filters

* Display the relative time on mouse hover

* Render journal entry times in ISO 8601 format

* Use ISO 8601 format when displaying dates & times in a table

* Standardize the use of DateTimeColumn across all tables

netbox/utilities/templates/builtins/customfield_value.html

@@ -9,9 +9,9 @@
 {% elif customfield.type == 'boolean' and value == False %}
   {% checkmark value false="False" %}
 {% elif customfield.type == 'date' and value %}
-  {{ value|annotated_date }}
+  {{ value|isodate }}
 {% elif customfield.type == 'datetime' and value %}
-  {{ value|annotated_date }}
+  {{ value|isodate }} {{ value|isodatetime }}
 {% elif customfield.type == 'url' and value %}
   <a href="{{ value }}">{{ value|truncatechars:70 }}</a>
 {% elif customfield.type == 'json' and value %}

netbox/utilities/templatetags/builtins/filters.py

@@ -5,6 +5,7 @@ import re
 import yaml
 from django import template
 from django.contrib.contenttypes.models import ContentType
+from django.contrib.humanize.templatetags.humanize import naturaltime
 from django.utils.html import escape
 from django.utils.safestring import mark_safe
 from markdown import markdown
@@ -20,6 +21,9 @@ __all__ = (
     'content_type',
     'content_type_id',
     'fgcolor',
+    'isodate',
+    'isodatetime',
+    'isotime',
     'linkify',
     'meta',
     'placeholder',
@@ -202,3 +206,36 @@ def render_yaml(value):
         {{ data_dict|yaml }}
     """
     return yaml.dump(json.loads(json.dumps(value)))
+
+
+#
+# Time & date
+#
+
+@register.filter()
+def isodate(value):
+    if type(value) is datetime.date:
+        text = value.isoformat()
+    elif type(value) is datetime.datetime:
+        text = value.date().isoformat()
+    else:
+        return ''
+    return mark_safe(f'<span title="{naturaltime(value)}">{text}</span>')
+
+
+@register.filter()
+def isotime(value, spec='seconds'):
+    if type(value) is datetime.time:
+        return value.isoformat(timespec=spec)
+    if type(value) is datetime.datetime:
+        return value.time().isoformat(timespec=spec)
+    return ''
+
+
+@register.filter()
+def isodatetime(value, spec='seconds'):
+    if type(value) is datetime.datetime:
+        text = f'{isodate(value)} {isotime(value, spec=spec)}'
+    else:
+        return ''
+    return mark_safe(f'<span title="{naturaltime(value)}">{text}</span>')