opened
wangguanquan
username_0
单元格格式为Time类型
```
org.ttzero.excel.reader.UncheckedTypeException: ConstantNumber 0.08702546296296296 can't convert to java.util.Date

	at org.ttzero.excel.util.DateUtil.toTimestamp(DateUtil.java:214)
	at org.ttzero.excel.reader.Row.toString(Row.java:1024)
	at java.lang.String.valueOf(String.java:2994)
	at java.io.PrintStream.println(PrintStream.java:821)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:184)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.ReferencePipeline$Head.forEach(ReferencePipeline.java:580)
	at java.util.stream.ReferencePipeline$7$1.accept(ReferencePipeline.java:270)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:481)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:471)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:151)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:174)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:418)
```
v0.4.2 row.toString 方法抛UncheckedTypeException
issue
closed
wangguanquan
username_0
issue