Document time.Truncate and time.Round

content/en/getting-started/glossary.md

@@ -32,6 +32,7 @@ weight: 60
 [U](#unmarshal) 
 [V](#variable) 
 [W](#walk) 
+[Z](#zero-time) 
 
 ###### action
 
@@ -446,3 +447,7 @@ Used to position an element within a collection sorted by weight. Assign weights
 ###### weighted page
 
 Contained within a [taxonomy object](#taxonomy-object), a weighted page is a [map](#map) with two elements: a `Page` object, and its [taxonomic weight](#taxonomic-weight) as defined in front matter. Access the elements using the `Page` and `Weight` keys.
+
+###### zero time
+
+The _zero time_ is January 1, 0001, 00:00:00 UTC. Formatted per [RFC3339](https://www.rfc-editor.org/rfc/rfc3339) the _zero time_ is 0001-01-01T00:00:00-00:00.

content/en/methods/time/Round.md

@@ -0,0 +1,24 @@
+---
+title: Round
+description: Returns the result of rounding TIME to the nearest multiple of DURATION since January 1, 0001, 00:00:00 UTC.
+categories: []
+keywords: []
+action:
+  related:
+    - functions/time/AsTime
+  returnType: time.Time
+  signatures: [TIME.Round DURATION]
+---
+
+The rounding behavior for halfway values is to round up.
+
+The `Round` method operates on TIME as an absolute duration since the [zero time]; it does not operate on the presentation form of the time. If DURATION is a multiple of one hour, `Round` may return a time with a non-zero minute, depending on the time zone.
+
+```go-html-template
+{{ $t := time.AsTime "2023-01-27T23:44:58-08:00" }}
+{{ $d := time.ParseDuration "1h"}}
+
+{{ ($t.Round $d).Format "2006-01-02T15:04:05-00:00" }} → 2023-01-28T00:00:00-00:00
+```
+
+[zero time]: /getting-started/glossary/#zero-time

content/en/methods/time/Truncate.md

@@ -0,0 +1,22 @@
+---
+title: Truncate
+description: Returns the result of rounding TIME down to a multiple of DURATION since January 1, 0001, 00:00:00 UTC.
+categories: []
+keywords: []
+action:
+  related:
+    - functions/time/AsTime
+  returnType: time.Time
+  signatures: [TIME.Truncate DURATION]
+---
+
+The `Truncate` method operates on TIME as an absolute duration since the [zero time]; it does not operate on the presentation form of the time. If DURATION is a multiple of one hour, `Truncate` may return a time with a non-zero minute, depending on the time zone.
+
+```go-html-template
+{{ $t := time.AsTime "2023-01-27T23:44:58-08:00" }}
+{{ $d := time.ParseDuration "1h"}}
+
+{{ ($t.Truncate $d).Format "2006-01-02T15:04:05-00:00" }} → 2023-01-27T23:00:00-00:00
+```
+
+[zero time]: /getting-started/glossary/#zero-time