tpl/time: Fix locale-specific month abbreviations

Closes #14948

tpl/time/time_integration_test.go

@@ -0,0 +1,53 @@
+// Copyright 2017 The Hugo Authors. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package time_test
+
+import (
+	"testing"
+
+	"github.com/gohugoio/hugo/hugolib"
+)
+
+// See issue 14948.
+func TestTimeFormatMonthAbbreviationsEnGB(t *testing.T) {
+	t.Parallel()
+
+	files := `
+-- hugo.toml --
+locale = 'en-GB'
+disableKinds = ['page','rss','section','sitemap','taxonomy','term']
+-- layouts/home.html --
+{{ $dates := slice
+	"2025-01-17T10:42:00-08:00"
+	"2025-02-17T10:42:00-08:00"
+	"2025-03-17T10:42:00-07:00"
+	"2025-04-17T10:42:00-07:00"
+	"2025-05-17T10:42:00-07:00"
+	"2025-06-17T10:42:00-07:00"
+	"2025-07-17T10:42:00-07:00"
+	"2025-08-17T10:42:00-07:00"
+	"2025-09-17T10:42:00-07:00"
+	"2025-10-17T10:42:00-07:00"
+	"2025-11-17T10:42:00-08:00"
+	"2025-12-17T10:42:00-08:00"
+}}
+{{- range $dates }}
+	{{- time.Format "Jan" . }}|
+{{- end }}
+`
+
+	b := hugolib.Test(t, files)
+
+	b.AssertFileContent("public/index.html", "Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sept|Oct|Nov|Dec|")
+}