"Time: the indefinite continued progress of existence and events in the past, present, and future regarded as a whole."
The fact that sometimes human beings can perceive time as different than it passes is proof it exists outside the human mind. When we perceive time inaccurately (like when something seems like it's taking forever, but a minute is still 60 seconds regardless) it only goes to show that time exists with or without our perception.
A tree does make a sound when it falls in the woods whether a human being is there to hear it or not. As such, time passes and trees grow in the woods whether a human is there to see that time progress. Time is like sound or wind. We cannot touch it, but it doesn't only exist in our minds, as evidenced by the fact that it still progresses with or without us. The measurements we use for it are in our minds, but time exists without those measurements too. I have never touched alpha centauri, but I know it's there because I can see it in a telescope. I have never actively watched my own hair grow, but I know it's up their doing it because it's longer than it was six months ago. Simple.
This is just a layman argument from my own thinking but...
A state of affairs that is progressively changing implies the existence of time. That is to say, the two different states of affairs cannot exist in two different states timelessly or simultaneously, therefore they must exist in two different temporal points.
Time can be easily conceptualized as the measurable unit for natural progression. This means that while "units of time" are made up no different than units of distance the distance itself and the process itself actually exists. To make it clear if it takes "two weeks" for a flower to grow this means that the flower does take some physical transformation within the world relative to the dilation that is measurable.
Time is an organizational tool humans made for sorting things, and as things progressed, time was 'refined' because of the structure of society, and it became slowly more and more important to get specific times. It is as real as any other invention, it's just a little more abstract than other inventions, but is still as real as a phone or the internet.
Time does exist, but it is only humans that measure time. Plants and animals grow and develop. After some time, they become 'adults' or fully developed. However, it is only humans who give time value and measure time. We alone create clocks, we alone check the seasons according to days, we alone measure the time we have on Earth.
Time exists in the minds of humans in that we have the concepts of past, present and future. However, time in itself may not actually exist. Think about this way. When looking at a certain colour (say red) the eye feeds information to the brain which creates how we see red (except in those with colour blindness). Time can be looked at in a similar way in that it is a concept created by the brain to prevent everything happening all at the same time, that allows us to make sense of the world. Whether time exists independently of humans is a question that cannot be answered, because we are all unfortunately stuck within the confines of the human brain.
Although ironically for us the past no longer exists, and the future has yet to exist, who can deny the now? For us 1 minute from now does not yet exist - but soon it will be your now. So until that moment, we are perceiving and experiencing creation moment by moment until that 1 minute is reached. Time has no physical location. It exist in, through, and around all things. So we are literally one with all time and all creation.