Although there are plenty of Visio alike products for UML diagrams, it's difficult to find a Visio alternative for Mac. To benefit Mac users, Edraw has newly released a Mac version allowing users to create uml diagram easily on Mac OS X system. It requires one-off payment instead of monthly or yearly fee while offers abundant free templates and examples.
The only way to bypass that error is to set the date to today's date and I did try a couple of suggested dates from 2016 through 2018. 
If you type 'date' you'll see whatever date your systems thinks it is. So, still stuck with a laptop that was working that is now imitating a brick.for Helder98 - when you get to therecovery screen - one of the dropdown menu tools is a command line window. As Narcinems noted, I change the date, download the installer and get as far as the screen to start installation, whereupon I get an error message that tells me to start all over again - and when I do I get the same issue. You can change the date by typing 'date mmddhhmmyy' i.e month day hour minute year two digits each.
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Download UML Diagram Software for Mac：
EdrawMax
All-in-One Diagram Software
- Superior file compatibility: Import and export drawings to various file formats, such as Visio
- Cross-platform supported (Windows, Mac, Linux, Web)
Visio Like UML Diagram Software for Mac
Edraw is a vector based UML Diagram creator having similar features with Visio that helps easily design uml diagram with ready-made symbols and templates. The Microsoft-like interface makes it quickly to get accustomed. Besides, there are much more uml symbols and templates than Visio, which will help you develop any UML diagram with no hassles. By using this Visio like tool, users can develop professional uml diagram in a way faster than you think.
Why Edraw is a Solid Visio Alternative for UML Diagram on Mac
Compare with Visio and many other diagramming tools, Edraw is a better choice for an array of benefits as follows.
Supported Diagrams
- Use-case diagram, class diagram, activity diagram and sequence diagram.
- Flowchart, organizational chart, mind map and over 20 kinds of diagrams.
Ease of Use
- A cheap Visio alternative that is much pore powerful than Visio.
- User-friendly interface similar with Word, without learning curve.
- Pre-made symbols that support drag-and-drop use.
- Pre-installed templates for instant start.
- A lightweight desktop app of flexible launch.
Cutting-edge Drawing Tools
- Supports direct links between pages.
- Nice drawing with automatic grid snap.
- Zoom in/out while keeping high resolution.
- Multiple diagram elements select and flexible Lasso Select Tool.
- Limitless drawing space with auto expansion.
- 1-click change of style through themes.
- Export diagrams to various formats such as graphics and MS documents.
Features Comparison Between Visio and Edraw
Easy Uml Tool
How to Create Perfect UML Diagram
UML Diagram can be easily created on Mac using Edraw. You can free download the trial version to see its powerful functions first. You will discover many practical uml diagram templates in the software, together with useful tutorial materials that help develop a perfect uml diagram smoothly.
- Start Edraw, open a uml diagram drawing type.
- The corresponding uml diagram symbols library will open automatically on the left, which contains the most common shapes for this certain uml diagram.
- Drag useful shapes and drop onto the canvas to start drawing.
- Connect shapes and style the shapes as you like.
- Lay out your uml diagram by using grid lines and quick Align and Distribute buttons.
- Apply a theme for professional quality result.
- When a uml diagram is done, many export options give you various choices to share your work in other formats.
Use the Software as Other Visio Alternatives for Mac:
Best Free Uml Tool For Mac
As an all-in-one Visio-like diagramming tool, it's not only capable for UML diagram, but also for floor plan, flowchart, electrical diagram, infographics, wireframe, science illustration, timeline, etc.