As other answers have pointed out - this would still be counted as "1 year experience". However, it will probably help you, to understand some of the reasons the years should be counted this way, and why it makes a difference to your employability.
Firstly, your experience in what you do is only going to grow over time. By being exposed to problems and solving them - your skillset will grow. Obviously, being at two employers may have helped you learn more than you would normally in 1 year of working; but you've still only had 365 (-weekends and holidays) of actual "on-the-job" experience in IT, and there's realistically a limit to how much you can have learned in that time.
Secondly, and often importantly in tech, many issues only appear over time. For example, projects may appear to run smoothly for the first 2 years and then fail to pass submission/compliance checking (due to earlier mistakes or oversight). If you've never seen this process from start to end, there are things you just will not be able to know/gain first-hand experience of.
Thirdly, similar to the above, there's a certain rate changes can be made. No matter how fast you work, other people are involved and even then - it takes time to measure the success of changes. As such, if you've only worked for a year - it's unlikely you've seen the real impact of any initiative you've started or improvements you've made (both positive and the problems you've caused).
Unfortunately, as above, there are just a number of things you will not have seen before in a single year of work (which are out of your control). This isn't your fault, or something you need to cover with study - but it does mean you are unlikely to have the same experience as somebody that has been in their role for 2 years (regardless of how you split the days between your two employers).