diff --git a/pkg/booking/ods.go b/pkg/booking/ods.go
index 1be8055..a319279 100644
--- a/pkg/booking/ods.go
+++ b/pkg/booking/ods.go
@@ -9,6 +9,7 @@ import (
 	"strings"
 	"time"
 
+	"dev.tandem.ws/tandem/camper/pkg/database"
 	"dev.tandem.ws/tandem/camper/pkg/locale"
 )
 
@@ -157,7 +158,7 @@ func writeCellString(sb *strings.Builder, s string) error {
 }
 
 func writeCellDate(sb *strings.Builder, t time.Time) {
-	sb.WriteString(fmt.Sprintf("          <table:table-cell table:style-name=\"ce1\" office:value-type=\"date\" office:date-value=\"%s\" calcext:value-type=\"date\"><text:p>%s</text:p></table:table-cell>\n", t.Format("2006-01-02"), t.Format("02/01/06")))
+	sb.WriteString(fmt.Sprintf("          <table:table-cell table:style-name=\"ce1\" office:value-type=\"date\" office:date-value=\"%s\" calcext:value-type=\"date\"><text:p>%s</text:p></table:table-cell>\n", t.Format(database.ISODateFormat), t.Format("02/01/06")))
 }
 
 func mustWriteOdsResponse(w http.ResponseWriter, ods []byte, filename string) {
diff --git a/pkg/database/db.go b/pkg/database/db.go
index 1efe16f..a2fa8a5 100644
--- a/pkg/database/db.go
+++ b/pkg/database/db.go
@@ -16,7 +16,9 @@ import (
 )
 
 const (
-	searchPathQuery = "set search_path to camper, public"
+	searchPathQuery   = "set search_path to camper, public"
+	ISODateFormat     = "2006-01-02"
+	ISODateTimeFormat = "2006-01-02 15:04:05"
 )
 
 func ErrorIsNotFound(err error) bool {
diff --git a/pkg/form/validator.go b/pkg/form/validator.go
index c7722bc..0673852 100644
--- a/pkg/form/validator.go
+++ b/pkg/form/validator.go
@@ -120,13 +120,13 @@ func (v *Validator) CheckValidPostalCode(ctx context.Context, conn *database.Con
 }
 
 func (v *Validator) CheckValidDate(field *Input, message string) bool {
-	_, err := time.Parse("2006-01-02", field.Val)
+	_, err := time.Parse(database.ISODateFormat, field.Val)
 	return v.Check(field, err == nil, message)
 }
 
 func (v *Validator) CheckDateAfter(field *Input, beforeField *Input, message string) bool {
-	date, _ := time.Parse("2006-01-02", field.Val)
-	before, _ := time.Parse("2006-01-02", beforeField.Val)
+	date, _ := time.Parse(database.ISODateFormat, field.Val)
+	before, _ := time.Parse(database.ISODateFormat, beforeField.Val)
 	return v.Check(field, date.After(before), message)
 }
 
diff --git a/pkg/season/admin.go b/pkg/season/admin.go
index b448203..bd6943a 100644
--- a/pkg/season/admin.go
+++ b/pkg/season/admin.go
@@ -204,7 +204,7 @@ func CollectSeasonCalendar(ctx context.Context, company *auth.Company, conn *dat
 		from generate_series($2, $3, interval '1 day') as t(day)
 		    left join season_calendar on season_range @> t.day::date
 		    left join season on season.season_id = season_calendar.season_id and company_id = $4
-	`, UnsetColor, firstDay.Format("2006-01-02 15:04:05"), lastDay.Format("2006-01-02 15:04:05"), company.ID)
+	`, UnsetColor, firstDay.Format(database.ISODateTimeFormat), lastDay.Format(database.ISODateTimeFormat), company.ID)
 	if err != nil {
 		return nil, err
 	}
diff --git a/pkg/template/render.go b/pkg/template/render.go
index 57314b4..3770c3b 100644
--- a/pkg/template/render.go
+++ b/pkg/template/render.go
@@ -23,6 +23,7 @@ import (
 
 	"dev.tandem.ws/tandem/camper/pkg/auth"
 	"dev.tandem.ws/tandem/camper/pkg/build"
+	"dev.tandem.ws/tandem/camper/pkg/database"
 	httplib "dev.tandem.ws/tandem/camper/pkg/http"
 )
 
@@ -104,7 +105,7 @@ func mustRenderLayout(w io.Writer, user *auth.User, company *auth.Company, templ
 			return formatPrice(price, user.Locale.Language, user.Locale.CurrencyPattern, company.DecimalDigits, company.CurrencySymbol)
 		},
 		"formatDate": func(time time.Time) template.HTML {
-			return template.HTML(`<time datetime="` + time.Format("2006-01-02") + `">` + time.Format("02/01/2006") + "</time>")
+			return template.HTML(`<time datetime="` + time.Format(database.ISODateFormat) + `">` + time.Format("02/01/2006") + "</time>")
 		},
 		"queryEscape": func(s string) string {
 			return url.QueryEscape(s)