Home›Guides›Every label in the job prints the same time (^FC, ^SL)
Every label in the job prints the same time (^FC, ^SL)
Published:
You print a job with more than one label and a clock field, and every
label carries the same time — even when the printer waited between
labels, for example in peel/dispenser mode. This is not a fault and not a
firmware bug: it is the documented default, and one ZPL parameter
changes it.
The cause: ^SL defaults to Start Time Mode
The ^FC command only declares the clock indicator
characters. When the clock is read is decided by a different
command, ^SL, and its default is S:
S — Start Time Mode: the time is read
“when label formatting begins (when ^XA is
received)”. The guide states the consequence plainly: the first
label has the same time placed on it as the last label.
T — Time Now Mode: the time is read “when
the label to be printed is placed in print queue”. The guide
compares it to a serialized time or date field.
So a job of ten labels printed under the default reads the clock
once. Nothing in ^FC can change that, which is why
adding more ^FC commands never helps.
Place ^SL inside the label format. With
^SLT, each label takes its time as it enters the print
queue, so a job that waits between labels no longer stamps them all
alike.
Accuracy tolerance (Enhanced Real Time Clock)
On printers with the Enhanced Real Time Clock (firmware
V60.13.0.10 or later) the mode parameter also accepts a number: a time
accuracy tolerance in seconds, range 1 to 999, where 0 means a
one-second tolerance. For example ^SL30,1 sets a
30-second tolerance and English as the language. The second parameter of
^SL is the language, not part of the timing.
Before any of this works: the RTC has to be there
The Real-Time Clock is a hardware option. The guide is explicit:
^FC is ignored if the Real Time Clock hardware is not
present, and the RTC commands apply only when the option is installed.
^FC must be included within each label field command
string every time clock values are required in that field — no date or
time can be printed in a field without it.
The substitution itself happens during the printing process:
^FD recognises the clock indicators and replaces them with
the time or date as the label prints.
Is one label per job the only way?
No. Splitting a ^PQ10 job into ten single-label
jobs is a workaround for the default mode, not a requirement of ZPL.
^SLT addresses the cause directly and keeps the job intact.
What a preview cannot tell you
Clock values are produced by the printer's own hardware at print time.
An online renderer — ours included — does not have that clock, so it
cannot show you what %H:%M:%S will become on paper. Use the
preview to check layout: where the field sits, whether it fits the
label, whether the font and rotation are right. The timing behaviour
itself is settled by ^SL, and by the printer.
We have not verified this on a physical printer; everything above is
what Zebra's own programming guide documents, cited by page below.
Sources
Zebra, ZPL II, ZBI 2, Set-Get-Do, Mirror, WML Programming Guide
(P1134473-11EN): ^SL — Set Mode and Language (for Real-Time Clock),
page 339; ^FC — Field Clock, page 189; Real Time Clock
appendix, pages 1613–1622.
Frequently asked questions
Why do all labels in one ZPL job show the same time?
Because ^SL defaults to Start Time Mode: the clock is read once, when label formatting begins. Zebra's guide says it outright — the first label has the same time placed on it as the last label (page 339).
Does adding more ^FC commands fix it?
No. ^FC only declares the clock indicator characters; it does not decide when the clock is read. That is ^SL's job, so the timing stays the same no matter how many ^FC commands the format contains.
Do I have to send one label per job?
No. Splitting the job works around the default mode but is not required by ZPL. ^SLT reads the clock as each label enters the print queue, so a single ^PQ job can carry different times.
Will this work on any Zebra printer?
Only where the Real-Time Clock option is installed. The guide states that ^FC is ignored when the RTC hardware is not present, and the accuracy-tolerance form of ^SL additionally needs the Enhanced Real Time Clock (V60.13.0.10 or later).
Can I see the printed time in an online preview?
No — the clock lives in the printer and the value is substituted during printing. A preview is the right tool for the field's position, size and rotation, not for what the clock will read.
