From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on inbox.vuxu.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=5.0 tests=MAILING_LIST_MULTI, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.4 Received: (qmail 23763 invoked from network); 9 Sep 2022 18:53:31 -0000 Received: from minnie.tuhs.org (50.116.15.146) by inbox.vuxu.org with ESMTPUTF8; 9 Sep 2022 18:53:31 -0000 Received: from minnie.tuhs.org (localhost [IPv6:::1]) by minnie.tuhs.org (Postfix) with ESMTP id 998D3422CC; Sat, 10 Sep 2022 04:53:10 +1000 (AEST) Received: from oclsc.com (oclsc.com [206.248.137.164]) by minnie.tuhs.org (Postfix) with ESMTP id 68D54422C9 for ; Sat, 10 Sep 2022 04:53:06 +1000 (AEST) Received: by oclsc.org id 11D814F1E1; Fri, 9 Sep 2022 14:53:05 -0400 (EDT) Received: by oclsc.org id 523C4640CDB; Fri, 9 Sep 2022 14:53:06 -0400 (EDT) To: tuhs@tuhs.org Message-ID: <45225B8CFC8D9179CB02A21EF7638288.for-standards-violators@oclsc.org> Date: Fri, 9 Sep 2022 14:53:06 -0400 (EDT) From: norman@oclsc.org (Norman Wilson) Message-ID-Hash: ESAU5QUIJZP6L7NZSWZEV2OZKICE6B2M X-Message-ID-Hash: ESAU5QUIJZP6L7NZSWZEV2OZKICE6B2M X-MailFrom: norman@oclsc.org X-Mailman-Rule-Misses: dmarc-mitigation; no-senders; approved; emergency; loop; banned-address; member-moderation; header-match-tuhs.tuhs.org-0; nonmember-moderation; administrivia; implicit-dest; max-recipients; max-size; news-moderation; no-subject; digests; suspicious-header X-Mailman-Version: 3.3.6b1 Precedence: list Subject: [TUHS] Re: Happy birthday, Unix timestamp! List-Id: The Unix Heritage Society mailing list Archived-At: List-Archive: List-Help: List-Owner: List-Post: List-Subscribe: List-Unsubscribe: Andrew Hume: if i recall correctly, V1 of Unix had time measured in milliseconds. were folks that sure that this would change before wrap-around? ==== Not milliseconds (which were infinitesimally small to the computers of 1969!) but clock ticks, 60 per second. Initially such times were stored in a pair of 18-bit PDP-7 words, giving a lifetime of about 36 years, so not so bad. The PDP-11's 16-bit words made that a 32-bit representation, or about two and a quarter years before overflow. Which explains why the time base was updated a few times in early days, then the representation changed to whole seconds, which in 32 bits would last about as long as 36 bits of 60 Hz ticks. The PDP-7 convention is documented only in the source code, so far as I know. The evolution of time on the PDP-11 can be tracked in time(II) in old manuals; the whole-seconds representation first appears in the Fourth Edition. Norman Wilson Toronto ON Not that old a timer, but once looked into old time