Setting issue start date on GANTT based on value selected

Hello Anton! 

This setup can, indeed, be achieved with a JS workflow. The field you need to set is whatever custom date field is configured as the Start date field in your Gantt chart's advanced settings, that's what the chart reads from each issue. You can verify or change this in your chart's settings, as described in our documentation at https://www.jetbrains.com/help/youtrack/cloud/configure-gantt-chart.html#gantt-advanced-settings.
 

The workflow code itself would be something like this: 

exports.rule = entities.Issue.onChange({
  title: 'Set Start Date from Quarter',
  guard: (ctx) => ctx.issue.fields.isChanged(ctx.Quarter),
  action: (ctx) => {
    const quarter = ctx.issue.fields.Quarter;
    if (!quarter) return;
    const match = quarter.name.match(/(\d{4})\s+Q(\d)/);
    if (!match) return;
    const year = parseInt(match[1]);
    const q = parseInt(match[2]);
    const monthStart = (q - 1) * 3;
    ctx.issue.fields.StartDate = new Date(year, monthStart, 1).getTime();
  },
  requirements: {
    Quarter: {
      type: entities.Field.enumType,
      name: 'Quarter'
    },
    StartDate: {
      type: entities.Field.dateType,
      name: 'Start Date'
    }
  }
});

A couple of things to adjust for your setup:

- The name in the Quarter requirement must match your field's exact name.

- The name in the StartDate requirement must match the date field configured as the Start date field in your Gantt chart.

- The regex assumes values follow a "YYYY Q#" format, adjust it if your values look different

There is one important caveat, unfortunately: there's currently a known bug where Gantt charts don't pick up date field changes made via workflows. The field value is updated on the issue itself, but the chart won't reflect it automatically; the same change made manually works fine. You can follow progress on this at JT-68746. Please feel free to vote for it - your vote helps us measure how many customers encounter this problem and automatically subscribes you to updates. To do so, sign in to JetBrains YouTrack and click the thumbs-up icon.

Please feel free to reach out anytime if any questions arise. Have a nice day! 

Thank you Stanislav Katsion , I tested and it works. Not sure if I understand the caveat correctly but I use a workflow to set my start date to the first working day of the quarter selected and this shows up just fine on my gantt

Hi Anton! 

Thank you for checking. You are right, I've now tested this on the latest build, and the start date changes on the issues in the Gantt chart. Likely, the issue was fixed, but the bug wasn't updated in the tracker. I'll ask the engineering team to update the bug in the tracker. 

Please don't hesitate to reach out anytime if you have any questions or need any assistance.