diff --git a/src/fns.js b/src/fns.js
index e0701132..dccb0ee6 100644
--- a/src/fns.js
+++ b/src/fns.js
@@ -76,7 +76,9 @@ exports.beADate = (d, s) => {
 }
 
 exports.formatTimezone = (offset, delimiter = '') => {
-  const absOffset = Math.abs(offset)
   const sign = offset > 0 ? '+' : '-'
-  return `${sign}${exports.zeroPad(absOffset)}${delimiter}00`
+  const absOffset = Math.abs(offset)
+  const hours = exports.zeroPad(parseInt('' + absOffset, 10))
+  const minutes = exports.zeroPad(absOffset % 1 * 60)
+  return `${sign}${hours}${delimiter}${minutes}`
 }
diff --git a/src/methods/format/_offset.js b/src/methods/format/_offset.js
index 03e51cad..75e3e7e0 100644
--- a/src/methods/format/_offset.js
+++ b/src/methods/format/_offset.js
@@ -5,32 +5,7 @@ const fns = require('../../fns')
 // "+01:00", "+0100", or simply "+01"
 const isoOffset = s => {
   let offset = s.timezone().current.offset
-  const isNegative = offset < 0
-  let minute = '00'
-  //handle 5.5 → '5:30'
-  if (Math.abs(offset % 1) === 0.5) {
-    minute = '30'
-    if (offset >= 0) {
-      offset = Math.floor(offset)
-    } else {
-      offset = Math.ceil(offset)
-    }
-  }
-  if (isNegative) {
-    //handle negative sign
-    offset *= -1
-    offset = fns.zeroPad(offset, 2)
-    offset = '-' + offset
-  } else {
-    offset = fns.zeroPad(offset, 2)
-    offset = '+' + offset
-  }
-  offset = offset + ':' + minute
-  //'Z' means 00
-  if (offset === '+00:00') {
-    offset = 'Z'
-  }
-  return offset
+  return !offset ? 'Z' : fns.formatTimezone(offset, ':')
 }
 
 module.exports = isoOffset