{"id":171,"date":"2026-10-08T13:21:37","date_gmt":"2026-10-08T12:21:37","guid":{"rendered":"http:\/\/genevatools.net\/?page_id=171"},"modified":"2026-10-08T18:28:18","modified_gmt":"2026-10-08T17:28:18","slug":"instructions","status":"publish","type":"page","link":"http:\/\/genevatools.net\/index.php\/instructions\/","title":{"rendered":"How TimeSynch Works"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">A Step By Step guide to using the tool and an explanation of the mechanics behind its time calculations<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How To Use The App<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Select your location.<\/strong> Choose your city from the first dropdown. The app auto-detects your browser&#8217;s timezone on load, but you can override it at any time.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Set the meeting time.<\/strong> Drag the slider (or type a value) to the time <em>in your timezone<\/em> when you want the meeting to start. The slider covers the full 24-hour day in 30-minute increments.<\/li>\n<\/ul>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Add participant timezones.<\/strong> Use the second dropdown to pick each participant&#8217;s city, then click <strong>Add<\/strong>. Repeat for as many people as you need. Your list is saved in your browser and persists between visits.<\/li>\n<\/ul>\n\n\n\n<ol class=\"wp-block-list\">\n<li><strong>Read the traffic-light results.<\/strong> Each participant&#8217;s box is colour-coded:<\/li>\n<\/ol>\n\n\n<div class=\"wp-block-image\">\n<figure class=\"aligncenter size-full is-resized\"><img loading=\"lazy\" decoding=\"async\" width=\"946\" height=\"345\" src=\"http:\/\/genevatools.net\/wp-content\/uploads\/2026\/10\/image.png\" alt=\"\" class=\"wp-image-226\" style=\"aspect-ratio:2.742157612853864;width:606px;height:auto\" srcset=\"http:\/\/genevatools.net\/wp-content\/uploads\/2026\/10\/image.png 946w, http:\/\/genevatools.net\/wp-content\/uploads\/2026\/10\/image-300x109.png 300w, http:\/\/genevatools.net\/wp-content\/uploads\/2026\/10\/image-768x280.png 768w\" sizes=\"auto, (max-width: 946px) 100vw, 946px\" \/><\/figure>\n<\/div>\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Remove a timezone by clicking the trash icon new to its row.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">How The Calculations Work<\/h2>\n\n\n\n<h3 class=\"wp-block-heading\">Accurate Time Offset Calculation<\/h3>\n\n\n\n<p class=\"wp-block-paragraph\">TimeSynch does not rely on a hardcoded offset table. Instead, it uses the browser&#8217;s built-in Intl.DateTimeFormat API with <strong>IANA timezone identifiers<\/strong> (e.g., Europe\/London, America\/New_York). These identifiers are backed by the IANA Time Zone Database, which is the same authoritative source used by operating systems, servers, and programming languages worldwide.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The process for each timezone is:<\/p>\n\n\n\n<ol class=\"wp-block-list\">\n<li>The app takes the meeting&#8217;s absolute UTC timestamp.<\/li>\n\n\n\n<li>It asks the browser: &#8220;What are the hour and minute <em>in this timezone<\/em> at that exact instant?&#8221;<\/li>\n\n\n\n<li>It reconstructs that local reading as a pseudo-UTC value and subtracts the original UTC value. The difference is the precise offset in minutes for that moment.<\/li>\n<\/ol>\n\n\n\n<p class=\"wp-block-paragraph\">Because the offset is computed <em>for the specific instant of the meeting<\/em>, it is always correct \u2014 whether that instant falls in winter or summer, before or after a DST transition.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Why this matters:<\/strong> A static table of &#8220;London = UTC+0&#8221; would be wrong for half the year. By querying the browser&#8217;s timezone engine at the exact meeting time, TimeSynch always gets the right answer.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Handling Calendar Day Boundaries<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">When a meeting at, say, 18:00 in London maps to 13:00 the <em>next<\/em> day in Sydney, the app handles this transparently:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Display:<\/strong> The time boxes show only the hour and minute (e.g., 13:00). The date is intentionally omitted because the traffic-light system is about <em>time of day<\/em>, not calendar date. A 13:00 in Sydney is a 13:00 regardless of whether it&#8217;s the same calendar day as London.<\/li>\n\n\n\n<li><strong>Calculation:<\/strong> The underlying math operates on absolute UTC millisecond timestamps, which are continuous and have no &#8220;day boundary.&#8221; Converting a UTC instant to a local time can wrap past midnight (e.g., 23:30 UTC \u2192 00:30 the next day in UTC+1), but the arithmetic is a simple addition\/subtraction of the offset \u2014 no special-case logic is needed.<\/li>\n\n\n\n<li><strong>Slider \u2192 UTC conversion:<\/strong> When you set the slider, the app reads your <em>local date<\/em> (year, month, day) in your timezone, combines it with the chosen hour\/minute, and converts to UTC. It performs this conversion <em>twice<\/em> (an iterative refinement) to guarantee correctness even if the offset itself changes between the first and second pass (see DST section below).<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><strong>Practical example:<\/strong> You set the slider to 22:00 in Europe\/London. For a participant in Australia\/Sydney (UTC+11), the box will show 09:00 \u2014 the next calendar day, but displayed simply as 09:00 in green.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Accounting for Daylight Savings Time (DST)<\/h2>\n\n\n\n<p class=\"wp-block-paragraph\">DST is handled entirely by the IANA timezone database via the browser&#8217;s Intl API. TimeSynch never hardcodes a DST rule. Here&#8217;s how it plays out in practice:<\/p>\n\n\n\n<ul class=\"wp-block-list\">\n<li><strong>Correct offset at the meeting time:<\/strong> If your meeting is on 15 March in America\/New_York, the browser returns UTC\u22125 (EST). If it&#8217;s on 15 April, it returns UTC\u22124 (EDT). No extra code is needed \u2014 the database encodes every historical and future transition for every zone.<\/li>\n\n\n\n<li><strong>Iterative refinement for edge cases:<\/strong> The slider-to-UTC conversion runs the offset lookup twice. This guards against the rare scenario where the first estimated UTC instant falls on one side of a DST boundary and the corrected instant falls on the other (e.g., a meeting scheduled at exactly 02:00 local time on the day clocks spring forward). The second pass re-queries the offset at the corrected instant and produces the final, accurate result.<\/li>\n\n\n\n<li><strong>Half-hour and 45-minute offsets:<\/strong> Zones like Australia\/Adelaide (UTC+9:30 \/ +10:30), Asia\/Kathmandu (UTC+5:45), and Pacific\/Marquesas (UTC\u22129:30) are handled identically \u2014 the offset is whatever the database says for that instant, in minutes, with no assumption of whole-hour increments.<\/li>\n\n\n\n<li><strong>Historical and future transitions:<\/strong> Because the IANA database is updated regularly by the browser, TimeSynch automatically reflects any government-announced DST changes (e.g., a country abolishing DST) without any code update on your part.<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n\n\n\n<h2 class=\"wp-block-heading\">Limitations and Notes<\/h2>\n\n\n\n<ul class=\"wp-block-list\">\n<li>The app does not display the calendar date for each timezone \u2014 only the time of day. If you need to confirm whether a meeting falls on the same or next day, compare the times: if the remote time is &#8220;earlier&#8221; than yours by more than ~12 hours, it&#8217;s likely the next day.<\/li>\n\n\n\n<li>The traffic-light ranges are set for commonly agreed working hours fixed and not adjustable.<\/li>\n\n\n\n<li>Saved timezones are stored in your browser&#8217;s local storage \u2014 they are per-device and per-browser, not synced across devices.<\/li>\n\n\n\n<li>The app requires a modern browser (Chrome 70+, Firefox 68+, Safari 14+, Edge 79+)<\/li>\n<\/ul>\n\n\n\n<p class=\"wp-block-paragraph\"><\/p>\n","protected":false},"excerpt":{"rendered":"<p>A Step By Step guide to using the tool and an explanation of the mechanics behind its time calculations How To Use The App Remove a timezone by clicking the trash icon new to its row. How The Calculations Work Accurate Time Offset Calculation TimeSynch does not rely on a [&hellip;]<\/p>\n","protected":false},"author":2,"featured_media":0,"parent":0,"menu_order":0,"comment_status":"closed","ping_status":"closed","template":"","meta":{"footnotes":""},"class_list":["post-171","page","type-page","status-publish","hentry"],"_links":{"self":[{"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/pages\/171","targetHints":{"allow":["GET"]}}],"collection":[{"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/pages"}],"about":[{"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/types\/page"}],"author":[{"embeddable":true,"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/comments?post=171"}],"version-history":[{"count":6,"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/pages\/171\/revisions"}],"predecessor-version":[{"id":249,"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/pages\/171\/revisions\/249"}],"wp:attachment":[{"href":"http:\/\/genevatools.net\/index.php\/wp-json\/wp\/v2\/media?parent=171"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}