diff --git a/format/date.js b/format/date.js
index 45091a34..983ab952 100644
--- a/format/date.js
+++ b/format/date.js
@@ -1,11 +1,21 @@
 'use strict'
 
-const {DateTime} = require('luxon')
+const {DateTime, IANAZone} = require('luxon')
 
+const timezones = new WeakMap()
+
+// todo: change to `(profile) => (when) => {}`
 const formatDate = (profile, when) => {
+	let timezone
+	if (timezones.has(profile)) timezone = timezones.get(profile)
+	else {
+		timezone = new IANAZone(profile.timezone)
+		timezones.set(profile, timezone)
+	}
+
 	return DateTime.fromMillis(+when, {
 		locale: profile.locale,
-		zone: profile.timezone
+		zone: timezone
 	}).toFormat('yyyyMMdd')
 }
 
diff --git a/format/time.js b/format/time.js
index d16b2e8c..c2474ee9 100644
--- a/format/time.js
+++ b/format/time.js
@@ -1,11 +1,21 @@
 'use strict'
 
-const {DateTime} = require('luxon')
+const {DateTime, IANAZone} = require('luxon')
 
+const timezones = new WeakMap()
+
+// todo: change to `(profile) => (when) => {}`
 const formatTime = (profile, when) => {
+	let timezone
+	if (timezones.has(profile)) timezone = timezones.get(profile)
+	else {
+		timezone = new IANAZone(profile.timezone)
+		timezones.set(profile, timezone)
+	}
+
 	return DateTime.fromMillis(+when, {
 		locale: profile.locale,
-		zone: profile.timezone
+		zone: timezone
 	}).toFormat('HHmmss')
 }
 
diff --git a/parse/date-time.js b/parse/date-time.js
index ec1fd849..9c777ad4 100644
--- a/parse/date-time.js
+++ b/parse/date-time.js
@@ -4,6 +4,7 @@ const {DateTime, IANAZone} = require('luxon')
 
 const timezones = new WeakMap()
 
+// todo: change to `(profile) => (date, time) => {}`
 const parseDateTime = (profile, date, time) => {
 	const pDate = [date.substr(-8, 4), date.substr(-4, 2), date.substr(-2, 2)]
 	if (!pDate[0] || !pDate[1] || !pDate[2]) {