Creating and updating gantt charts can be done with various tools and software such as Microsoft Project, Excel, PowerPoint, Google Sheets, Trello, Asana, and Smartsheet. To create and update a gantt chart, you should first define the project scope, objectives, and deliverables. Then list all project tasks and subtasks in a table or spreadsheet. Estimate the duration, start date, and end date of each task and subtask. Identify the dependencies and constraints among the tasks and subtasks. Assign resources and responsibilities for each task and subtask. Create a bar chart showing tasks and subtasks horizontally and time vertically. Adjust the length, position, and color of the bars to reflect duration, start date, end date, and status of each task/subtask. Add milestones, indicators, labels, and legends to enhance readability/clarity of your gantt chart. Review/validate your gantt chart with stakeholders/team members. Lastly, update your gantt chart regularly as your project progresses or changes occur.