title: What is the best practice of store datetime in a database?
body: <p>I am working on buy order table for store client's record from frontend side and my case:</p>
  <ol>
  <li>Client would which come from different countries, different timezones</li>
  <li>My database server timezone is on UTC+1</li>
  <li>Daylight saving time might apply in some countries</li>
  <li>Some clients might buy a product from country A, then buy another product from country B the next day but on different timezones</li>
  <li>Some client (travelers) which come from country A (UTC+2) and bought items in country B (UTC+0) via his phone (UTC+3, I don't know why but they are)</li>
  </ol>
  <p>Here are my questions:</p>
  <ol>
  <li>What is the best practice to store the datetime in the database?</li>
  <li>Does frontend side need to convert timezones from client to database?</li>
  <li>Does backend side need to convert timezones from database to client? How do I determine a client's current timezone?</li>
  <li>What is the best practice to show datetime from server to website for client review?</li>
  <li><strong>(New)</strong> How do I handle <code>available_delivery_date</code> and <code>available_delivery_time</code> which those fields input by client?</li>
  </ol>
  <p>==================</p>
  <p><strong>[ Update 1 ]</strong>
  An addition description about question point 5, my order table have 2 fields named <code>available_delivery_date</code> and <code>available_delivery_time</code> which input by client with their timezone, what is the best practice to save the record?</p>