title: R: lubridate with ts() gives wrong date
body: <p>I am working with some data from the FRED and I try to convert the data to a time series with weekly observation. I use the following code:</p>
  <pre><code>library(quantmod)
  library(lubridate)
  getSymbols('WALCL',src='FRED')
  assets &lt;- ts(WALCL, frequency = 365.25/7, end = decimal_date(ymd(&quot;2020-07-15&quot;)))
  </code></pre>
  <p>But instead of the end date being set to 2020-07-15 it is always set to 2021 and the start date to 2003  instead of 2002. The same thing happens when I specify the start date instead. When I try to specify both I get the error <code>Error in attr(data, &quot;tsp&quot;) &lt;- c(start, end, frequency) :  invalid time series parameters specified</code>.</p>
  <p>Is there something obvious I am missing or is there an error with the data I downloaded or with <code>lubridate</code>?</p>