Why we recommend right-aligned content
Use of right-alignment enhances the neatness and organization of your résumé.
Recruiters may take 20 to 30 seconds on the first go-round to visually scan your résumé. If you present information to them in well-assembled visual bits that fit a predictable pattern, they will find your document easier to use - and that ease of use will contribute to the overall, positive impression you are trying to make.
What you did and where you did it (title and organization) have more importance in the hierarchy of information than the location and dates. In English, information placed on the left side of the page will be read before information on the right side of the page.
It is also likely that you will present your experience under headings that group by types of experience, rather than in straight, reverse chronological order, in which case the dates do not function as a primary piece of information.
When résumés are being reviewed by a person (as opposed to a computer), too much information ganged together can slow up the visual scan of the résumé, and slow up the time it takes to separate and process the information. When you separate the title and company names from the dates and locations by a restful dose of white space, in a predictable pattern on the page, you give the reviewer's eye and brain well-organized access to easily-processed chunks of information, with a predetermined hierarchy of importance.
Why put the location and dates on at all, you might ask. Good question! When you did the tasks, fulfilled the responsibilities, and achieved accomplishments is important because it speaks to how up-to-date your skills are; how recently you exhibited a habit of leadership, achievement, and teamwork (or other positive qualities); and of course, how recently you were employed in a relevant field. Where geographically you did it speaks to the depth and breadth of your professional and cultural background.
There are times when vertical space considerations might not allow the right alignment of dates and places. For example, you might need to adjust the formatting to reflect the dates and places in one line across the page.
Always plan for the ease of your end user.
If the style you use to format a résumé will be subjected to a human, visual scan, the basic advice is to make the formatting consistent throughout the document and therefore predictable. Based on your first few entries on the résumé, the reviewing eye and brain are assembling predictions about how and where they will find information on the rest of the page.
If your résumé information is orderly and systematic, the reviewer will acquire your information in an orderly and systematic way, making the job of assessing you easier and happier. Your work will impress them as orderly, systematic, and effective. In contrast: if your information is presented in a new way with each entry, that makes information retrieval a more involved and labor-intensive process for the reviewer, and you may be perceived as unreliable, disorganized and ineffective.