Snowflake • inspect the timestamp contract — Choose an explicit conversion signature and preserve the distinction between an unzoned wall-clock result and a zone-offset timestamp,…

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<header><span class="eyebrow">Typed timestamp lab / January 15, 2024</span><h1>The clock is only half the result.</h1><p class="intro">Compare three fixed contracts and inspect the logical value, offset, and returned type.</p></header>
<nav class="controls" aria-label="Conversion case"><button type="button" id="c1" class="secondary">C1 · explicit NTZ</button><button type="button" id="c2" class="secondary">C2 · offset TZ</button><button type="button" id="c3" class="secondary">C3 · session NTZ</button></nav>
<section class="result"><span class="eyebrow">Expected logical result • local arithmetic</span><div class="big" id="result">2024-01-15 12:00:00</div><div class="type-line"><b id="result-type">TIMESTAMP_NTZ</b><span id="offset">No attached offset</span></div><p id="rule">Three arguments: explicit UTC source, UTC target.</p><p id="trace" class="trace"></p></section>
<div class="grid"><section class="panel"><h2 id="case-title">C1 · Wall clock → wall clock</h2><label for="clock">Input wall-clock time (HH:MM)</label><input id="clock" type="text" value="12:00"><p id="input-type" class="muted">Explicit TIMESTAMP_NTZ · date fixed at 2024-01-15.</p><div id="offset-input" hidden><label for="input-offset">Input UTC offset (±HHMM)</label><input id="input-offset" type="text" value="+0200"></div><div id="session-input" hidden><label class="inline"><input type="checkbox" id="session">Use the declared fixture session TIMEZONE = UTC</label><small>This declares an assumption; it does not set or verify a Snowflake session.</small></div><label class="inline"><input type="checkbox" id="null-target">Use a SQL NULL target argument</label><div class="controls"><button type="button" id="calculate">Calculate expectation</button><button type="button" id="reset" class="secondary">Reset fixtures</button></div><p id="error" class="error" role="alert"></p></section>
<section class="panel"><h2>Native SELECT specification</h2><label for="sql">Generated SQL — manual copying</label><textarea id="sql" class="code" readonly rows="8"></textarea><div class="controls"><button type="button" id="select-sql" class="secondary">Select text</button></div><small>Select the exact SQL, then copy it manually to your authorized native workflow.</small></section></div>
<section class="panel"><h2>Same noon, different evidence</h2><div class="table-wrap"><table><thead><tr><th>Case</th><th>Original expected value</th><th>Return type</th><th>Source rule</th></tr></thead><tbody><tr><td>C1</td><td>12:00, no offset</td><td>NTZ</td><td>Explicit UTC argument</td></tr><tr><td>C2</td><td>10:00 +0000</td><td>TZ</td><td>Noon +0200 input</td></tr><tr><td>C3</td><td>12:00 +0000</td><td>TZ</td><td>Declared UTC session</td></tr></tbody></table></div></section>
<details><summary>Keep native evidence separate</summary><p>Record the actual input type, logical result, output formatting, session TIMEZONE, environment/version, source revision, and any subsequent cast. Determine the active TZDB release on the authorized instance with SYSTEM$GET_TZDB_VERSION; availability and results are unobserved here.</p><label for="native-notes">Native observations (optional, not saved)</label><textarea id="native-notes" placeholder="Leave blank until observed on your instance."></textarea></details>
<footer>A bounded HTML companion, not a Snowflake runtime. UTC-only source/target fixtures and explicit numeric offsets are supported; no IANA/DST ambiguity policy is inferred. NULL is distinct from invalid input. Expected display is logical notation, not captured Snowflake formatting or native type evidence.</footer>
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let caseId='c1';
function timestampExpectation(which,clock,offset,session,isNull){if(!/^(?:[01]\d|2[0-3]):[0-5]\d$/.test(clock))throw Error('Enter a valid 24-hour time as HH:MM.');let minutes=0;if(which==='c2'){if(!/^[+-](?:0\d|1[0-4])[0-5]\d$/.test(offset)||(/^[-+]14/.test(offset)&&!offset.endsWith('00')))throw Error('Use an offset from -1400 through +1400, with valid minutes.');minutes=(Number(offset.slice(1,3))*60+Number(offset.slice(3)))*(offset[0]==='-'?-1:1)}if(which==='c3'&&!session)throw Error('Declare the UTC session assumption for C3; an unknown session cannot be inferred.');if(isNull)return {value:'NULL',type:'NULL',offset:'No timestamp value',trace:'A SQL NULL argument produces NULL.'};const [h,m]=clock.split(':').map(Number),date=new Date(Date.UTC(2024,0,15,h,m)-minutes*60000);return {value:date.toISOString().slice(0,19).replace('T',' '),type:which==='c1'?'TIMESTAMP_NTZ':'TIMESTAMP_TZ',offset:which==='c1'?'No attached offset':'+0000',trace:which==='c2'?clock+' '+offset+' represents the same instant as '+date.toISOString().slice(11,16)+' UTC.':which==='c1'?'Wall-clock fields unchanged; source UTC is an argument, not attached metadata.':'NTZ is interpreted using the declared UTC session.'}}
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