title: Error in as.POSIXct.numeric(value) : 'origin' must be supplied in ggplot
body: <p>I'm currently analyzing a dataset of GSR values.
  I first had to transform my unix values into readable data and then create a plot of the GSR values in function of time.</p>
  
  <p>That is how the dataset looks like:
  <a href="https://i.stack.imgur.com/cbqWb.png" rel="noreferrer"><img src="https://i.stack.imgur.com/cbqWb.png" alt="enter image description here"></a></p>
  
  <p>This is my code and graph<a href="https://i.stack.imgur.com/BIgvs.png" rel="noreferrer"><img src="https://i.stack.imgur.com/BIgvs.png" alt="enter image description here"></a>:</p>
  
  <pre><code>veranda &lt;- ggplot(gsr_veranda, aes(as.POSIXct(Date, origin = "1970-01-01"), Values)) +
                 geom_line() +
                 scale_x_datetime(date_labels = "%H:%M:%s") +
  </code></pre>
  
  <p>I wanted to zoom into the graph and look at a specific time I tried this code:</p>
  
  <pre><code>veranda &lt;- ggplot(gsr_veranda, aes(as.POSIXct(Date, origin = "1970-01-01"), Values)) +
                 geom_line() +
                 scale_x_datetime(date_labels = "%H:%M:%s") +
                 scale_x_continuous(limits = c("11:05:02", "11:05:03"))
  </code></pre>
  
  <p>However, I still get this error:
  Error in as.POSIXct.numeric(value) : 'origin' must be supplied</p>
  
  <p>But the origin was already supplied when I transformed my unix into readable data and again in my ggplot code.</p>
  
  <p>How can I fix this?</p>