om<span class="op">=</span><span class="fu"><a href="https://rdrr.io/r/base/as.POSIXlt.html" class="external-link">as.POSIXct</a></span><span class="op">(</span><span class="st">"2021-06-30 00:15"</span><span class="op">)</span>, to<span class="op">=</span><span class="fu"><a href="https://rdrr.io/r/base/as.POSIXlt.html" class="external-link">as.POSIXct</a></span><span class="op">(</span><span class="st">"2021-06-30 23:45"</span><span class="op">)</span>, by<span class="op">=</span><span class="st">"15 min"