ISO INTERNATIONAL STANDARD 8601-1 First edition 2019-02 Date and time Representations for information interchange Part 1: Basic rules Date et heure - Représentations pour I'échange d'information - Partie 1: Regles debase Reference number IS0 8601-1:2019(E) ISO @ IS0 2019 IS0 8601-1:2019(E) COPYRIGHTPROTECTEDDOCUMENT @ ISO 2019 All rights reserved. Unless otherwise specified, or required in the context of its implementation, no part of this publication may be reproduced or utilized otherwise in any form or by any means, electronic or mechanical, including photocopying, or posting on the internet or an intranet, without prior written permission. Permission can be requested from either IsO at the address below or Iso's member body in the country of the requester. ISO copyright office CP 401 : Ch. de Blandonnet 8 CH-1214 Vernier, Geneva Phone: +4122 749 0111 Fax: +41 22 749 09 47 Email: copyright@iso.org Website: www.iso.org Published in Switzerland ii @ IS0 2019 - All rights reserved IS0 8601-1:2019(E) Contents Page Foreword ..V Introduction. ..vii 1 Scope. 2 Normative references 3 Terms, definitions and symbols. 3.1 Terms and definitions ..1 3.1.1 Basic concepts. 3.1.2 Time and date units ..5 3.1.3 Representations and formats. 3.2 Symbols .10 3.2.1 General ..10 3.2.2 Time scale component symbols. ..10 3.2.3 Composite component symbols. .11 3.2.4 Symbols used in place of digits or signs ..11 3.2.5 Designator symbols. ..12 3.2.6 Separator symbols ..13 4 Fundamental principles. .13 4.1 Basic rules. .13 4.2 Timescales .13 4.2.1 The Gregorian calendar .13 4.2.2 The week calendar. .14 4.2.3 The 24-hour clock .15 4.3 Time scale components and units .15 4.3.1 General. .15 4.3.2 Calendar year and years duration .15 4.3.3 Calendar month and months duration. ..16 4.3.4 Calendar week number and weeks duration .16 4.3.5 Calendar day of month and days duration. ..16 4.3.6 Calendar day of week. ..16 4.3.7 Calendar day of year ..17 4.3.8 Clock hour and hours duration. .17 4.3.9 Clock minute and minutes duration ..17 4.3.10 Clock second and seconds duration ..17 4.3.11 Decade. .18 4.3.12 Century. .18 4.3.13 Time shift. .18 4.4 Expansion.. .18 4.5 Leading zeros ..19 5 Date and time representations .19 5.1 General .19 5.2 Date. ..19 5.2.1 General. .19 5.2.2 Calendardate .19 5.2.3 Ordinal date. 21 5.2.4 Week date.. .21 5.3 Time of day. .22 5.3.1 Local time of day 22 5.3.2 Beginning of the day 24 5.3.3 UTC of day.... 24 5.3.4 Local time scale and UTC 24 5.3.5 Omissions of time designator .25 5.4 Date and time of day. .25 IS0 2019 - All rights reserved iii