diff --git a/docs/custom-api.md b/docs/custom-api.md
index 566aa58..49502e6 100644
--- a/docs/custom-api.md
+++ b/docs/custom-api.md
@@ -447,6 +447,8 @@ The following helper functions provided by Glance are available:
 - `concat(strings ...string) string`: Concatenates multiple strings together.
 - `unique(key string, arr []JSON) []JSON`: Returns a unique array of JSON objects based on the given key.
 - `percentChange(current float, previous float) float`: Calculates the percentage change between two numbers.
+- `startOfDay(t time.Time) time.Time`: Returns the start of the day for a given time.
+- `endOfDay(t time.Time) time.Time`: Returns the end of the day for a given time.
 
 The following helper functions provided by Go's `text/template` are available:
 
diff --git a/internal/glance/widget-custom-api.go b/internal/glance/widget-custom-api.go
index e9c744f..3d94eb6 100644
--- a/internal/glance/widget-custom-api.go
+++ b/internal/glance/widget-custom-api.go
@@ -509,6 +509,12 @@ var customAPITemplateFuncs = func() template.FuncMap {
 			// Shorthand to do both of the above with a single function call
 			return dynamicRelativeTimeAttrs(customAPIFuncParseTimeInLocation(layout, value, time.UTC))
 		},
+		"startOfDay": func(t time.Time) time.Time {
+			return time.Date(t.Year(), t.Month(), t.Day(), 0, 0, 0, 0, t.Location())
+		},
+		"endOfDay": func(t time.Time) time.Time {
+			return time.Date(t.Year(), t.Month(), t.Day(), 23, 59, 59, 0, t.Location())
+		},
 		// The reason we flip the parameter order is so that you can chain multiple calls together like this:
 		// {{ .JSON.String "foo" | trimPrefix "bar" | doSomethingElse }}
 		// instead of doing this: