diff --git a/src/formats.ts b/src/formats.ts
index 594cddf..46f1192 100644
--- a/src/formats.ts
+++ b/src/formats.ts
@@ -149,33 +149,27 @@ function compareDate(d1: string, d2: string): number | undefined {
   return 0
 }
 
-const TIME = /^(\d\d):(\d\d):(\d\d)(\.\d+)?(z|[+-]\d\d(?::?\d\d)?)?$/i
-const PLUS_MINUS = /^[+-]/
-const TIMEZONE = /^[Zz]$/
-const ISO_8601_TIME = /^[+-](?:[01][0-9]|2[0-4])(?::?[0-5][0-9])?$/
+const TIME = /^(\d\d):(\d\d):(\d\d(?:\.\d+)?)(z|([+-]\d\d)(?::?(\d\d))?)?$/i
 
-function time(str: string, withTimeZone?: boolean, strict?: boolean): boolean {
+function time(str: string, withTimeZone?: boolean, strictTime?: boolean): boolean {
   const matches: string[] | null = TIME.exec(str)
   if (!matches) return false
-
-  const hour: number = +matches[1]
-  const minute: number = +matches[2]
-  const second: number = +matches[3]
-  const timeZone: string = matches[5]
+  const hr: number = +matches[1]
+  const min: number = +matches[2]
+  const sec: number = +matches[3]
+  const tz: string | undefined = matches[4]
+  const tzH: number = +(matches[5] || 0)
+  const tzM: number = +(matches[6] || 0)
   return (
-    ((hour <= 23 && minute <= 59 && second <= 59) ||
-      (hour === 23 && minute === 59 && second === 60)) &&
-    (!withTimeZone ||
-      (strict
-        ? TIMEZONE.test(timeZone) ||
-          (PLUS_MINUS.test(timeZone) && time(timeZone.slice(1) + ":00")) ||
-          ISO_8601_TIME.test(timeZone)
-        : timeZone !== ""))
+    ((hr <= 23 && min <= 59 && sec < 60 && tzH <= 24 && tzM < 60) ||
+      // leap second
+      (hr - tzH === 23 && min - tzM === 59 && sec < 61 && tzH <= 24 && tzM < 60)) &&
+    (!withTimeZone || (tz !== "" && (!strictTime || !!tz)))
   )
 }
 
-function strict_time(str: string, withTimeZone?: boolean): boolean {
-  return time(str, withTimeZone, true)
+function strict_time(str: string): boolean {
+  return time(str, true, true)
 }
 
 function compareTime(t1: string, t2: string): number | undefined {
@@ -183,23 +177,22 @@ function compareTime(t1: string, t2: string): number | undefined {
   const a1 = TIME.exec(t1)
   const a2 = TIME.exec(t2)
   if (!(a1 && a2)) return undefined
-  t1 = a1[1] + a1[2] + a1[3] + (a1[4] || "")
-  t2 = a2[1] + a2[2] + a2[3] + (a2[4] || "")
+  t1 = a1[1] + a1[2] + a1[3]
+  t2 = a2[1] + a2[2] + a2[3]
   if (t1 > t2) return 1
   if (t1 < t2) return -1
   return 0
 }
 
 const DATE_TIME_SEPARATOR = /t|\s/i
-function date_time(str: string): boolean {
+function date_time(str: string, strictTime?: boolean): boolean {
   // http://tools.ietf.org/html/rfc3339#section-5.6
   const dateTime: string[] = str.split(DATE_TIME_SEPARATOR)
-  return dateTime.length === 2 && date(dateTime[0]) && time(dateTime[1], true)
+  return dateTime.length === 2 && date(dateTime[0]) && time(dateTime[1], true, strictTime)
 }
 
 function strict_date_time(str: string): boolean {
-  const dateTime: string[] = str.split(DATE_TIME_SEPARATOR)
-  return dateTime.length === 2 && date(dateTime[0]) && strict_time(dateTime[1], true)
+  return date_time(str, true)
 }
 
 function compareDateTime(dt1: string, dt2: string): number | undefined {
diff --git a/src/index.ts b/src/index.ts
index dece7e6..9550b15 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -18,7 +18,7 @@ export interface FormatOptions {
   mode?: FormatMode
   formats?: FormatName[]
   keywords?: boolean
-  strictDate?: boolean
+  strictTime?: boolean
 }
 
 export type FormatsPluginOptions = FormatName[] | FormatOptions
@@ -32,7 +32,7 @@ const fastName = new Name("fastFormats")
 
 const formatsPlugin: FormatsPlugin = (
   ajv: Ajv,
-  opts: FormatsPluginOptions = {keywords: true, strictDate: false}
+  opts: FormatsPluginOptions = {keywords: true, strictTime: false}
 ): Ajv => {
   if (Array.isArray(opts)) {
     addFormats(ajv, opts, fullFormats, fullName)
@@ -41,7 +41,7 @@ const formatsPlugin: FormatsPlugin = (
   const [formats, exportName] =
     opts.mode === "fast" ? [fastFormats, fastName] : [fullFormats, fullName]
   const list = opts.formats || formatNames
-  addFormats(ajv, list, opts.strictDate ? {...formats, ...strictFormats} : formats, exportName)
+  addFormats(ajv, list, opts.strictTime ? {...formats, ...strictFormats} : formats, exportName)
   if (opts.keywords) formatLimit(ajv)
   return ajv
 }
diff --git a/tests/strictDate.spec.ts b/tests/strictTime.spec.ts
similarity index 90%
rename from tests/strictDate.spec.ts
rename to tests/strictTime.spec.ts
index 91e3091..4c7034a 100644
--- a/tests/strictDate.spec.ts
+++ b/tests/strictTime.spec.ts
@@ -2,9 +2,9 @@ import Ajv from "ajv"
 import addFormats from "../dist"
 
 const ajv = new Ajv({$data: true, strictTypes: false, formats: {allowedUnknown: true}})
-addFormats(ajv, {strictDate: true})
+addFormats(ajv, {mode: "full", strictTime: true})
 
-describe("strictDate option", () => {
+describe("strictTime option", () => {
   it("a valid date-time string with time offset", () => {
     expect(
       ajv.validate(